Related to https://projects.blender.org/blender/blender/pulls/147994 in
which clang-cl builds failed passing the Windows SDK libraries paths to
the compiler.
The previous CMake implementation tried to reverse engineer these paths
at CMake configuration time but failed with `clang-cl`.
The environment variables set by vcvars that could have been useful
aren't always available when cmake is called, so now we keep the `LIB`
environment variable intact at compile time and pass the other
additional compiler libraries paths - that are better defined at CMake
configuration time - separately through `-L` compiler arguments.
Pull Request: https://projects.blender.org/blender/blender/pulls/148035
3753c70b9c