CMake: Workaround fix for failing RC file generation on Windows

For some reason the Help target doesn't get its RC file generated
when building qttools, which leads to a build failure.

We don't quite know yet why all this is happening, but a workaround
fix seems to be to use an OBJECT library instead of an INTERFACE
library to propagate the generated RC file.

Amends 657fa0462d

Fixes: QTBUG-84155
Change-Id: I1e1c2f3b05bae2ed009020d031c6510a517c01ec
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/corelib/Qt6CoreMacros.cmake

@@ -969,8 +969,7 @@ END
             # We would like to do the following:
             #     target_sources(${target} PRIVATE "$<$<CONFIG:${cfg}>:${output}>")
             # However, https://gitlab.kitware.com/cmake/cmake/-/issues/20682 doesn't let us.
-            add_library(${target}_${cfg}_rc INTERFACE)
-            target_sources(${target}_${cfg}_rc INTERFACE "${output}")
+            add_library(${target}_${cfg}_rc OBJECT "${output}")
             target_link_libraries(${target} PRIVATE "$<$<CONFIG:${cfg}>:${target}_${cfg}_rc>")
         endwhile()
     endif()