Blender Git Loki

Fix: Building with clang on windows.

The USD landing broke building with clang on windows
due to a couple of reasons:

1) Some incompatibilities in their headers [1] only one
of them was important for us and is included in our patchset
now.

2) clangs lld wanted the full path to the libusd_b library
when using the whole archive link option, while msvc can
figure it out from just the library name.

Tested with clang/msvc and msbuild and ninja generators

[1] https://github.com/PixarAnimationStudios/USD/issues/1030