[GWP-ASan] Disable GWP-ASan on Android for now.

Summary:
Temporarily disable GWP-ASan for android until the bugs at:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-android/builds/87
... can be fixed. See comments for the full bug trace.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: srhines, kubamracek, mgorny, cryptoad, jfb, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D63460

llvm-svn: 363624