[compiler-rt/asan] Disable irrelevant unittest on win64

Summary:
This test is allocating a 1gig chunk to make shadow allocation failed,
but on 64-bits architecture the test is working.

Reviewers: rnk

Subscribers: kubabrecka, llvm-commits, wang0109, chrisha

Differential Revision: https://reviews.llvm.org/D22553

llvm-svn: 276122