cmd/go: add darwin/arm64 in the list of supported systems in help message

Fixes #49173.

Change-Id: I71270b4ff7e9ede3cdfa5946b73142a731752adf
Reviewed-on: https://go-review.googlesource.com/c/go/+/358901
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 8178073..9d8c321 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -114,7 +114,7 @@
 // 		The default is GOMAXPROCS, normally the number of CPUs available.
 // 	-race
 // 		enable data race detection.
-// 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64, windows/amd64,
+// 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64, darwin/arm64, windows/amd64,
 // 		linux/ppc64le and linux/arm64 (only for 48-bit VMA).
 // 	-msan
 // 		enable interoperation with memory sanitizer.
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index ffe33bf..9d0ad27 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -68,7 +68,7 @@
 		The default is GOMAXPROCS, normally the number of CPUs available.
 	-race
 		enable data race detection.
-		Supported only on linux/amd64, freebsd/amd64, darwin/amd64, windows/amd64,
+		Supported only on linux/amd64, freebsd/amd64, darwin/amd64, darwin/arm64, windows/amd64,
 		linux/ppc64le and linux/arm64 (only for 48-bit VMA).
 	-msan
 		enable interoperation with memory sanitizer.