fix: CMake include path and QString literals

- Add target_include_directories for test target to find MainWindow.h
- Replace u""_s literals with QStringLiteral() for compiler compatibility
- Fixes Jenkins build errors

Entire-Checkpoint: 0e6491fe1b1c

qt6-after/qt6-migrated-benchmark/CMakeLists.txt

@@ -66,6 +66,10 @@ add_executable(Qt6MigratedBenchmarkTest
     MainWindow.cpp
 )
 
+target_include_directories(Qt6MigratedBenchmarkTest PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+)
+
 target_link_libraries(Qt6MigratedBenchmarkTest PRIVATE
     Qt6::Core
     Qt6::Gui