Add NOMINMAX to PlatformCommonInternal

By not explicitly disabling min/max macros of `windows.h`, we may see
some unintended substitutions. This is especially important now that we
are moving toward enabling Unity Build, and some of the constructs for
manually dealing with this issue, eg., `#ifdef max`, `#undef max`, might
not make it to the pool, and as a result we get build failure.

Pick-to: 6.5
Change-Id: Ie3c31aebe00300126a2ac3a6044876ab92d5d99c
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

cmake/QtHeadersClean.cmake

@@ -184,6 +184,9 @@ function(qt_internal_add_headersclean_target module_target module_headers)
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
         set(hcleanFLAGS -std:c++latest -Zc:__cplusplus -Za -WX -W3 -EHsc)
 
+        # Because we now add `-DNOMINMAX` to `PlatformCommonInternal`.
+        set(hcleanUDEFS -UNOMINMAX)
+
         # cl.exe needs a source path
         get_filename_component(source_path "${QT_MKSPECS_DIR}/features/data/dummy.cpp" REALPATH)
 
@@ -194,6 +197,7 @@ function(qt_internal_add_headersclean_target module_target module_headers)
             "${hcleanFLAGS}"
             "${target_includes_joined_genex}"
             "${hcleanDEFS}"
+            "${hcleanUDEFS}"
         )
         string(JOIN " " compiler_command_line_variables
             "-FI"

cmake/QtInternalTargets.cmake

@@ -170,6 +170,8 @@ if(WIN32)
     # Needed for M_PI define. Same as mkspecs/features/qt_module.prf.
     # It's set for every module being built, but it's not propagated to user apps.
     target_compile_definitions(PlatformModuleInternal INTERFACE _USE_MATH_DEFINES)
+    # Not disabling min/max macros may result in unintended substitutions of std::min/max
+    target_compile_definitions(PlatformCommonInternal INTERFACE NOMINMAX)
 endif()
 if(FEATURE_largefile AND UNIX)
     target_compile_definitions(PlatformCommonInternal