Make Sure that `qml_compile_hash_p.h` Isn't Missing

In the event of an unexpected build directory corruption, CMake
may fail to replace/install the `qml_compiler_hash_p.h` properly.

I have had similar errors with other files missing as well, so this
fix might be applicable to elsewhere as well.

Pick-to: 6.4
Change-Id: Ife3e28a09296b5428d0f0248648caabda601c94d
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

cmake/QtDeclarativeSetup.cmake

@@ -10,6 +10,8 @@
 function(qt_declarative_write_tag_header target_name)
     set(out_file "${CMAKE_CURRENT_BINARY_DIR}/qml_compile_hash_p.h")
     if(FEATURE_developer_build AND EXISTS "${out_file}")
+        target_sources(${target_name} PRIVATE "${out_file}")
+        set_source_files_properties("${out_file}" PROPERTIES GENERATED TRUE)
         return()
     endif()