[compiler-rt][TSan] Add TSan runtime support for Go on linux-aarch64.

Summary:
This patch adds TSan runtime support for Go on linux-aarch64
platforms. This enables people working on golang to implement their
platform/language part of the TSan support.

Basic testing is done with lib/tsan/go/buildgo.sh. Additional testing will be
done as part of the work done in the Go project.

It is intended to support other VMA sizes, except 39 which does not
have enough bits to support the Go heap requirements.

Patch by Fangming Fang <Fangming.Fang@arm.com>.

Reviewers: kubamracek, dvyukov, javed.absar

Subscribers: mcrosier, dberris, mgorny, kristof.beyls, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D52167

llvm-svn: 342541