runtime/race: add race detector support for linux/riscv64

runtime/race: add race detector support for linux/riscv64

This enables support for the race detector on linux/riscv64.

Fixes #64345

Cq-Include-Trybots: luci.golang.try:gotip-linux-riscv64
Change-Id: I98962827e91455404858549b0f9691ee438f104b
Reviewed-on: https://go-review.googlesource.com/c/go/+/690497
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>