[COFF, ARM64] Add support for Windows ARM64 COFF format

Summary: This is the clang part of the initial implementation to support Windows ARM64 COFF format.

Reviewers: ruiu, t.p.northover, rnk, compnerd

Reviewed By: ruiu, compnerd

Subscribers: aemerson, kristof.beyls, cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D34706

llvm-svn: 306489