VS: Redundant definition in CMAKE_RC_FLAGS
The /DWIN32 definition is already present in CMAKE_C(XX)_FLAGS
and is inherited from there. A simple experiment shows that removing this define from CMAKE_RC_FLAGS cache value does not change the output except for flags rearrangement. So
it can be removed from the defaults. This way we probably would not need the code which eliminate duplicate defines.
In the same spirit, /D_DEBUG can be moved from CMAKE_RC_FLAGS_DEBUG
to CMAKE_C(XX)_FLAGS_DEBUG
, where it IMHO belongs.