runtime, cmd: support race detector on darwin/arm64

https://reviews.llvm.org/D90435 is the counterpart in LLVM TSAN.

race_linux_arm64.syso is built with LLVM commit
00da38ce2d36c07f12c287dc515d37bb7bc410e9 on a macOS/ARM64 machine.
(It is not built on a builder with golang.org/x/build/cmd/racebuild
as we don't have darwin/arm64 builder for now.)

Updates #38485.

Change-Id: I391efdacd9480197e308370bfccd05777deb4aee
Reviewed-on: https://go-review.googlesource.com/c/go/+/266373


Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>