Implement flock for Windows in compiler-rt

Summary:
This patch implements flock for Windows, needed to make gcda writing work in a multiprocessing scenario.

Fixes https://bugs.llvm.org/show_bug.cgi?id=34923.

Reviewers: zturner

Reviewed By: zturner

Subscribers: rnk, zturner, llvm-commits

Differential Revision: https://reviews.llvm.org/D38891

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@317705 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed