[compiler-rt][asan] Turn on ASAN unittests for win64.

Summary:
Asan is now working on windows 64-bit.
This patch is turning on the unittest.

Reviewers: rnk

Reviewed By: rnk

Subscribers: kubamracek, dberris, beanz, mgorny, llvm-commits, chrisha

Differential Revision: https://reviews.llvm.org/D24742

llvm-svn: 296878