GetModuleHandleW is a "desktop apps only" API. We avoid calling it for OneCore:

and so we can't load GetTempPath2W for OneCore and must always use the GetTempPathW fallback instead:

winapisupp.cpp is built into the STL's DLL, and the non-dllexported __crtGetTempPath2W is used by filesys.cpp in the DLL, implementing the non-Standard/highly-deprecated <experimental/filesystem>.

For Standard <filesystem>, we inject filesystem.cpp into the STL's import LIB, but we weren't similarly guarding GetModuleHandleW. (This is the only other call in the STL.) Somehow, nobody has hissed about <filesystem> being incompatible with UWP apps, but I suspect maybe nobody happened to be calling temp_directory_path() in their UWP apps, and so the linker discarded this unused machinery from the import lib. In any event, we should fix the code to be consistent and avoid potential problems for UWP.