Better clang support on Windows
Better clang support on Windows

1. Add clang lib/ and include/ path in `LIB` and `INCLUDE` environment variable
2. Fallback to msvc linker and lib.exe if the clang toolchain doesn't provide them.

Closes #6801.

Change-Id: Ifcd4b27a6968b57311ecbb04c47880f9126808ff
PiperOrigin-RevId: 223780642

dslomov/bazel,bazelbuild/bazel,dslomov/bazel-windows,bazelbuild/bazel,katre/bazel,meteorcloudy/bazel,perezd/bazel,werkt/bazel,dslomov/bazel,dslomov/bazel-windows,ButterflyNetwork/bazel,werkt/bazel,aehlig/bazel,ButterflyNetwork/bazel,perezd/bazel,katre/bazel,davidzchen/bazel,cushon/bazel,bazelbuild/bazel,safarmer/bazel,dslomov/bazel,safarmer/bazel,werkt/bazel,dslomov/bazel-windows,ulfjack/bazel,cushon/bazel,perezd/bazel,katre/bazel,werkt/bazel,davidzchen/bazel,ulfjack/bazel,davidzchen/bazel,davidzchen/bazel,aehlig/bazel,werkt/bazel,ulfjack/bazel,twitter-forks/bazel,akira-baruah/bazel,twitter-forks/bazel,werkt/bazel,cushon/bazel,meteorcloudy/bazel,meteorcloudy/bazel,dslomov/bazel,davidzchen/bazel,katre/bazel,ulfjack/bazel,aehlig/bazel,dslomov/bazel,cushon/bazel,dslomov/bazel-windows,safarmer/bazel,aehlig/bazel,aehlig/bazel,katre/bazel,meteorcloudy/bazel,dslomov/bazel,safarmer/bazel,ulfjack/bazel,bazelbuild/bazel,safarmer/bazel,ButterflyNetwork/bazel,perezd/bazel,ButterflyNetwork/bazel,akira-baruah/bazel,bazelbuild/bazel,safarmer/bazel,twitter-forks/bazel,dslomov/bazel-windows,ButterflyNetwork/bazel,twitter-forks/bazel,cushon/bazel,twitter-forks/bazel,katre/bazel,akira-baruah/bazel,twitter-forks/bazel,perezd/bazel,dslomov/bazel-windows,perezd/bazel,aehlig/bazel,perezd/bazel,davidzchen/bazel,ulfjack/bazel,meteorcloudy/bazel,twitter-forks/bazel,aehlig/bazel,akira-baruah/bazel,ulfjack/bazel,davidzchen/bazel,cushon/bazel,bazelbuild/bazel,akira-baruah/bazel,akira-baruah/bazel,meteorcloudy/bazel,ButterflyNetwork/bazel,dslomov/bazel,meteorcloudy/bazel