[OpenMP] Don't hardcode _WIN32_WINNT for MinGW targets (#115708)
Instead respect what the toolchain default is (or what the user sets via
CMAKE_CXX_FLAGS).
This fixes builds with libcxx, with mingw toolchains targeting
msvcrt.dll, after 5d8be4c036aa5ce4a94f1f37a9155d5c877e23db; after that
commit, the libcxx public headers reference symbols such as iswspace_l,
which are unavailable when targeting msvcrt.dll on older versions of
Windows (it's only available in msvcrt.dll since Windows Vista).
GitOrigin-RevId: dc3156d8e6dc6494bc47ba074d0c990eb27b7564
1 file changed
