qmake: make unity-buildable

msvc_objectmodel.cpp and qmakeparser.cpp have symbols that may clash.
Removing them from unity builds allows qmake to be unity-built.

Pick-to: 6.5
Change-Id: I46443ec979142ab2ebb686f9444b37e1043f0af1
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 72f5793)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 5ef06fd)

qmake/CMakeLists.txt

@@ -58,7 +58,6 @@ qt_internal_add_tool(${target_name}
     TRY_RUN
     TOOLS_TARGET Core
     USER_FACING
-    NO_UNITY_BUILD
     INSTALL_VERSIONED_LINK
     SOURCES
         cachekeys.h
@@ -99,6 +98,9 @@ qt_internal_add_tool(${target_name}
         "qmake_pch.h"
     LIBRARIES
         QtLibraryInfo
+    NO_UNITY_BUILD_SOURCES
+        generators/win32/msvc_objectmodel.cpp # xml symbols clash with generators/win32/msbuild_objectmodel.cpp
+        library/qmakeparser.cpp               # struct statics clashes with qmakeevaluator_p.h
 )
 qt_internal_return_unless_building_tools()