Set the meson command to use when we know what it isnirbheek/rework-meson-script-handling

Instead of using fragile guessing to figure out how to invoke meson,
set the value when meson is run. Also rework how we pass of
meson_script_launcher to regenchecker.py -- it wasn't even being used

With this change, we only need to guess the meson path when running
the tests, and in that case:

1. If MESON_EXE is set in the env, we know how to run meson
   for project tests.
2. MESON_EXE is not set, which means we run the configure in-process
   for project tests and need to guess what meson to run, so either
   - meson.py is found next to run_tests.py, or
   - meson, meson.py, or meson.exe is in PATH

Otherwise, you can invoke meson in the following ways:

1. meson is installed, and mesonbuild is available in PYTHONPATH:
   - meson, meson.py, meson.exe from PATH
   - python3 -m mesonbuild.mesonmain
   - python3 /path/to/meson.py
   - meson is a shell wrapper to meson.real
2. meson is not installed, and is run from git:
   - Absolute path to meson.py
   - Relative path to meson.py
   - Symlink to meson.py

All these are tested in test_meson_commands.py, except meson.exe since
that involves building the meson msi and installing it.

1 files changed, 3 insertions, 3 deletions

diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index fc837d6f9..4bcffbdab 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -262,10 +262,9 @@ class Environment:
     private_dir = 'meson-private'
     log_dir = 'meson-logs'
 
-    def __init__(self, source_dir, build_dir, main_script_launcher, options, original_cmd_line_args):
+    def __init__(self, source_dir, build_dir, options, original_cmd_line_args):
         self.source_dir = source_dir
         self.build_dir = build_dir
-        self.meson_script_launcher = main_script_launcher
         self.scratch_dir = os.path.join(build_dir, Environment.private_dir)
         self.log_dir = os.path.join(build_dir, Environment.log_dir)
         os.makedirs(self.scratch_dir, exist_ok=True)
@@ -278,7 +277,8 @@ class Environment:
             # re-initialized with project options by the interpreter during
             # build file parsing.
             self.coredata = coredata.CoreData(options)
-            self.coredata.meson_script_launcher = self.meson_script_launcher
+            # Used by the regenchecker script, which runs meson
+            self.coredata.meson_command = mesonlib.meson_command
             self.first_invocation = True
         if self.coredata.cross_file:
             self.cross_info = CrossBuildInfo(self.coredata.cross_file)