embedded: Add some long-pending notes about prefixes

This is pretty essential for anyone doing cross compilation.

Change-Id: If831b5875d912ac6f0223428a018d2deb1bd0068
Reviewed-by: Andy Nichols <andy.nichols@theqtcompany.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/src/platforms/emb-linux.qdoc b/doc/src/platforms/emb-linux.qdoc
index 1a2dd660..099fffb7 100644
--- a/doc/src/platforms/emb-linux.qdoc
+++ b/doc/src/platforms/emb-linux.qdoc
@@ -89,6 +89,21 @@
   machine before running \c configure. Otherwise, the Qt build may attempt to
   use inappropriate headers and libraries from the host system.
 
+  Specifying \c -sysroot results in automatically setting the \c --sysroot
+  argument when invoking the compiler. In some cases this is not desirable and
+  can be disabled by passing \c -no-gcc-sysroot to \c configure.
+
+  \c -prefix, \c -extprefix and \c -hostprefix control the intended destination
+  directory of the Qt build. In the above example the ARM build of Qt is
+  expected to be placed in \c{/usr/local/qt5} on the target device. Note that
+  running \c{make install} does not deploy anything to the device. Instead, the
+  \c install step targets the directory specified by \c extprefix which defaults
+  to \c sysroot + \c prefix and is therefore optional. However, in many cases
+  "polluting" the sysroot is not desirable and thus specifying \c -extprefix
+  becomes important. Finally, \c -hostprefix allows separating host tools like
+  qmake, rcc, uic from the binaries for the target. When given, such tools will
+  be installed under the specified directory instead of \c extprefix.
+
   See \l {Qt Configure Options} for more information.
 
   \section1 Platform Plugins for Embedded Linux Devices