Optionally include ${repo}Setup.cmake file in qt_build_repo_begin

This is meant to keep repo specific functions and macros that should
not pollute QtSetup.cmake. For example QtDeclarativeSetup.cmake
will automatically be included when building qtdeclarative.

Change-Id: I4d26cbb1a7ffafb153a888fc918af337000d5e41
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Qt CMake Build Bot

cmake/QtBuildInternals/QtBuildInternalsConfig.cmake

@@ -33,6 +33,9 @@ macro(qt_build_repo_begin)
     # Qt specific setup common for all modules:
     include(QtSetup)
     include(FeatureSummary)
+
+    # Optionally include a repo specific Setup module.
+    include(${PROJECT_NAME}Setup OPTIONAL)
 endmacro()
 
 macro(qt_build_repo_end)