Disable Unity Build for Examples

Pick-to: 6.5
Task-number: QTBUG-109394
Change-Id: I20999512e557db618c14e36d62317680bc17c43a
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtBuildInternals/QtBuildInternalsConfig.cmake

@@ -848,6 +848,8 @@ macro(qt_examples_build_begin)
 
     cmake_parse_arguments(arg "${options}" "${singleOpts}" "${multiOpts}" ${ARGN})
 
+    set(CMAKE_UNITY_BUILD OFF)
+
     # Use by qt_internal_add_example.
     set(QT_EXAMPLE_BASE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
 
@@ -984,6 +986,8 @@ macro(qt_examples_build_end)
 # Restore backed up CMAKE_INSTALL_PREFIX.
 set(CMAKE_INSTALL_PREFIX \"\${_qt_internal_examples_cmake_install_prefix_backup}\")
 ")
+
+    set(CMAKE_UNITY_BUILD ${QT_UNITY_BUILD})
 endmacro()
 
 function(qt_internal_add_example subdir)