libclang building statically on Windows

Hi,

I have a review at https://reviews.llvm.org/D75068 which adds support for building

libclang statically on Windows.

This is a squash of two previous reviews which got merged and then reverted due to

issues found post-commit.

I have addressed the troublesome issues and it has been two months since I await a

review, any help in getting this forward is appreciated.

Cheers,

Cristian.