meson: add option to skip installing to $sysconfdir

This is useful for development where overwriting files out side
the configured prefix will affect the host as well as stateless
systems such as NixOS that don't let packages install to /etc but handle
configuration on their own.

Alternative to https://github.com/systemd/systemd/pull/17501

tested with:

$ mkdir inst build && cd build
$ meson \
  -Dcreate-log-dirs=false \
  -Dsysvrcnd-path=$(realpath ../inst)/etc/rc.d \
  -Dsysvinit-path=$(realpath ../inst)/etc/init.d \
  -Drootprefix=$(realpath ../inst) \
  -Dinstall-sysconfdir=false \
  --prefix=$(realpath ../inst) ..
$ ninja install

13 files changed, 71 insertions, 42 deletions

diff --git a/src/core/meson.build b/src/core/meson.build
index 552590393d..77767eb603 100644
--- a/src/core/meson.build
+++ b/src/core/meson.build
@@ -192,12 +192,14 @@ in_files = [['macros.systemd',   rpmmacrosdir],
 foreach item : in_files
         file = item[0]
         dir = item[1]
+        if install_sysconfdir or dir != pkgsysconfdir
+                configure_file(
+                        input : file + '.in',
+                        output : file,
+                        configuration : substs,
+                        install_dir : dir == 'no' ? '' : dir)
+        endif
 
-        configure_file(
-                input : file + '.in',
-                output : file,
-                configuration : substs,
-                install_dir : dir == 'no' ? '' : dir)
 endforeach
 
 install_data('org.freedesktop.systemd1.conf',
@@ -217,6 +219,8 @@ meson.add_install_script('sh', '-c', mkdir_p.format(systemsleepdir))
 meson.add_install_script('sh', '-c', mkdir_p.format(systemgeneratordir))
 meson.add_install_script('sh', '-c', mkdir_p.format(usergeneratordir))
 
-meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'system')))
-meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'user')))
-meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(sysconfdir, 'xdg/systemd')))
+if install_sysconfdir
+        meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'system')))
+        meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'user')))
+        meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(sysconfdir, 'xdg/systemd')))
+endif
diff --git a/src/coredump/meson.build b/src/coredump/meson.build
index 663c6c7a07..ebd99bd379 100644
--- a/src/coredump/meson.build
+++ b/src/coredump/meson.build
@@ -13,7 +13,7 @@ endif
 
 coredumpctl_sources = files('coredumpctl.c')
 
-if conf.get('ENABLE_COREDUMP') == 1
+if conf.get('ENABLE_COREDUMP') == 1 and install_sysconfdir
         install_data('coredump.conf',
                      install_dir : pkgsysconfdir)
 endif
diff --git a/src/home/meson.build b/src/home/meson.build
index 7847449c43..e3cc1a9fb5 100644
--- a/src/home/meson.build
+++ b/src/home/meson.build
@@ -107,8 +107,10 @@ if conf.get('ENABLE_HOMED') == 1
         install_data('org.freedesktop.home1.policy',
                      install_dir : polkitpolicydir)
 
-        install_data('homed.conf',
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data('homed.conf',
+                             install_dir : sysconfdir)
+        endif
 endif
 
 tests += [
diff --git a/src/journal-remote/meson.build b/src/journal-remote/meson.build
index 66cbcc69df..4572f4bd1c 100644
--- a/src/journal-remote/meson.build
+++ b/src/journal-remote/meson.build
@@ -48,8 +48,10 @@ if conf.get('ENABLE_REMOTE') ==1 and conf.get('HAVE_LIBCURL') == 1
                 input : 'journal-upload.conf.in',
                 output : 'journal-upload.conf',
                 configuration : substs)
-        install_data(journal_upload_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(journal_upload_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 endif
 
 if conf.get('ENABLE_REMOTE') == 1 and conf.get('HAVE_MICROHTTPD') == 1
@@ -57,8 +59,10 @@ if conf.get('ENABLE_REMOTE') == 1 and conf.get('HAVE_MICROHTTPD') == 1
                 input : 'journal-remote.conf.in',
                 output : 'journal-remote.conf',
                 configuration : substs)
-        install_data(journal_remote_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(journal_remote_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 
         install_data('browse.html',
                      install_dir : join_paths(pkgdatadir, 'gatewayd'))
diff --git a/src/journal/meson.build b/src/journal/meson.build
index 520e33c0b8..7aea28d129 100644
--- a/src/journal/meson.build
+++ b/src/journal/meson.build
@@ -107,8 +107,10 @@ journalctl_sources = files('''
         pcre2-dlopen.h
 '''.split())
 
-install_data('journald.conf',
-             install_dir : pkgsysconfdir)
+if install_sysconfdir
+        install_data('journald.conf',
+                     install_dir : pkgsysconfdir)
+endif
 
 if get_option('create-log-dirs')
         meson.add_install_script(
diff --git a/src/kernel-install/meson.build b/src/kernel-install/meson.build
index 851e827590..4117188f14 100644
--- a/src/kernel-install/meson.build
+++ b/src/kernel-install/meson.build
@@ -3,16 +3,19 @@
 want_kernel_install = get_option('kernel-install')
 
 if want_kernel_install
-	install_data('kernel-install',
-		install_mode : 'rwxr-xr-x',
-		install_dir : bindir)
+        install_data('kernel-install',
+                     install_mode : 'rwxr-xr-x',
+                     install_dir : bindir)
 
-	install_data('00-entry-directory.install',
-		'50-depmod.install',
-		'90-loaderentry.install',
-		install_mode : 'rwxr-xr-x',
-		install_dir : kernelinstalldir)
+        install_data('00-entry-directory.install',
+                     '50-depmod.install',
+                     '90-loaderentry.install',
+                     install_mode : 'rwxr-xr-x',
+                     install_dir : kernelinstalldir)
+
+        if install_sysconfdir
+                meson.add_install_script('sh', '-c',
+                                         mkdir_p.format(join_paths(sysconfdir, 'kernel/install.d')))
+        endif
 
-	meson.add_install_script('sh', '-c',
-				mkdir_p.format(join_paths(sysconfdir, 'kernel/install.d')))
 endif
diff --git a/src/login/meson.build b/src/login/meson.build
index fd3202cd98..e09610960b 100644
--- a/src/login/meson.build
+++ b/src/login/meson.build
@@ -74,8 +74,10 @@ if conf.get('ENABLE_LOGIND') == 1
                 input : 'logind.conf.in',
                 output : 'logind.conf',
                 configuration : substs)
-        install_data(logind_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(logind_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 
         install_data('org.freedesktop.login1.conf',
                      install_dir : dbuspolicydir)
diff --git a/src/network/meson.build b/src/network/meson.build
index cd1a897199..f5ca183088 100644
--- a/src/network/meson.build
+++ b/src/network/meson.build
@@ -236,8 +236,10 @@ if conf.get('ENABLE_NETWORKD') == 1
                              install_dir : polkitpkladir)
         endif
 
-        install_data('networkd.conf',
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data('networkd.conf',
+                             install_dir : pkgsysconfdir)
+        endif
 
         fuzzers += [
     [['src/network/fuzz-netdev-parser.c',
diff --git a/src/oom/meson.build b/src/oom/meson.build
index a250d2a62a..e966ad1dd8 100644
--- a/src/oom/meson.build
+++ b/src/oom/meson.build
@@ -29,6 +29,8 @@ if conf.get('ENABLE_OOMD') == 1
         install_data('org.freedesktop.oom1.service',
                      install_dir : dbussystemservicedir)
 
-        install_data('oomd.conf',
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data('oomd.conf',
+                             install_dir : sysconfdir)
+        endif
 endif
diff --git a/src/pstore/meson.build b/src/pstore/meson.build
index 3b3a37c777..6c0ab0563b 100644
--- a/src/pstore/meson.build
+++ b/src/pstore/meson.build
@@ -4,7 +4,7 @@ systemd_pstore_sources = files('''
         pstore.c
 '''.split())
 
-if conf.get('ENABLE_PSTORE') == 1
+if conf.get('ENABLE_PSTORE') == 1 and install_sysconfdir
         install_data('pstore.conf',
                      install_dir : pkgsysconfdir)
 endif
diff --git a/src/resolve/meson.build b/src/resolve/meson.build
index eb6fabea95..8e7bad0659 100644
--- a/src/resolve/meson.build
+++ b/src/resolve/meson.build
@@ -169,8 +169,10 @@ if conf.get('ENABLE_RESOLVE') == 1
                 input : 'resolved.conf.in',
                 output : 'resolved.conf',
                 configuration : substs)
-        install_data(resolved_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(resolved_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 
         install_data('resolv.conf',
                      install_dir : rootlibexecdir)
diff --git a/src/timesync/meson.build b/src/timesync/meson.build
index 22b6347bab..571e3fc7ef 100644
--- a/src/timesync/meson.build
+++ b/src/timesync/meson.build
@@ -26,8 +26,10 @@ if conf.get('ENABLE_TIMESYNCD') == 1
                 input : 'timesyncd.conf.in',
                 output : 'timesyncd.conf',
                 configuration : substs)
-        install_data(timesyncd_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(timesyncd_conf,
+                             install_dir : pkgsysconfdir)
+        endif
         install_data('org.freedesktop.timesync1.conf',
                      install_dir : dbuspolicydir)
         install_data('org.freedesktop.timesync1.service',
diff --git a/src/udev/meson.build b/src/udev/meson.build
index e6dd4c7cac..5eb0f994a5 100644
--- a/src/udev/meson.build
+++ b/src/udev/meson.build
@@ -185,8 +185,10 @@ foreach prog : [['ata_id/ata_id.c'],
                    install_dir : udevlibexecdir)
 endforeach
 
-install_data('udev.conf',
-             install_dir : join_paths(sysconfdir, 'udev'))
+if install_sysconfdir
+        install_data('udev.conf',
+                     install_dir : join_paths(sysconfdir, 'udev'))
+endif
 
 configure_file(
         input : 'udev.pc.in',
@@ -194,8 +196,10 @@ configure_file(
         configuration : substs,
         install_dir : pkgconfigdatadir == 'no' ? '' : pkgconfigdatadir)
 
-meson.add_install_script('sh', '-c',
-                         mkdir_p.format(join_paths(sysconfdir, 'udev/rules.d')))
+if install_sysconfdir
+        meson.add_install_script('sh', '-c',
+                                 mkdir_p.format(join_paths(sysconfdir, 'udev/rules.d')))
+endif
 
 fuzzers += [
         [['src/udev/net/fuzz-link-parser.c',