Avoid collecting dependencies from modules that were explicitly skipped

If either -skip <module> or BUILD_<module>=OFF is set from command line
we should avoid processing the module dependencies and exclude it from
the list of modules that needs to be build.

Change-Id: Ieec8db085221cc4abd5d8ac83c06ecce25d5d4b0
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
(cherry picked from commit 13a7e25f5d)

CMakeLists.txt

@@ -29,16 +29,26 @@ include(ECMOptionalAddSubdirectory)
 
 qt_internal_top_level_before_build_submodules()
 
+qt_internal_find_modules(known_submodules)
 # Get submodule list if not already defined
 if(NOT QT_BUILD_SUBMODULES)
     if(DEFINED ENV{QT_BUILD_SUBMODULES})
         set(QT_BUILD_SUBMODULES "$ENV{QT_BUILD_SUBMODULES}")
     else()
-        qt_internal_find_modules(QT_BUILD_SUBMODULES)
+        set(QT_BUILD_SUBMODULES "${known_submodules}")
     endif()
 endif()
 set(QT_BUILD_SUBMODULES "${QT_BUILD_SUBMODULES}" CACHE STRING "Submodules to build")
 
+# Preliminary check if module should be skipped since -skip <module> or BUILD_<module>
+# are provided.
+set(explicitly_skipped_modules "")
+foreach(module IN LISTS known_submodules)
+    if(DEFINED BUILD_${module} AND NOT BUILD_${module})
+        list(APPEND explicitly_skipped_modules ${module})
+    endif()
+endforeach()
+
 foreach(module IN LISTS QT_BUILD_SUBMODULES)
     if(NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${module}/CMakeLists.txt)
         message(FATAL_ERROR
@@ -48,7 +58,8 @@ foreach(module IN LISTS QT_BUILD_SUBMODULES)
     endif()
 endforeach()
 
-qt_internal_sort_module_dependencies("${QT_BUILD_SUBMODULES}" QT_BUILD_SUBMODULES)
+qt_internal_sort_module_dependencies("${QT_BUILD_SUBMODULES}" QT_BUILD_SUBMODULES
+    SKIP_MODULES ${explicitly_skipped_modules})
 
 foreach(module IN LISTS QT_BUILD_SUBMODULES)
     # Check for unmet dependencies