[compiler-rt] Set asan win 64-bits to use dynamic address for memory allocator

Summary:
ASAN on Windows 64-bits should use a dynamic address instead of a fixed one.
The asan-allocator code to support dynamic address is already landed.
This patch is turning on the feature.

Reviewers: rnk

Subscribers: kubabrecka, dberris, llvm-commits, chrisha

Differential Revision: https://reviews.llvm.org/D24575

llvm-svn: 281522