cmd/dist: enable race detector test on Linux/ARM64

CL 138675 added the race detector support on Linux/ARM64, but it
didn't enable the race detector tests in cmd/dist (therefore in
all.bash). Enable them.

Updates #28848

Change-Id: I4306dad2fb4167021d568436076b9f535d7f6e07
Reviewed-on: https://go-review.googlesource.com/c/149967
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/test.go

@@ -1471,7 +1471,7 @@ func (t *tester) packageHasBenchmarks(pkg string) bool {
 func raceDetectorSupported(goos, goarch string) bool {
 	switch goos {
 	case "linux":
-		return goarch == "amd64" || goarch == "ppc64le"
+		return goarch == "amd64" || goarch == "ppc64le" || goarch == "arm64"
 	case "darwin", "freebsd", "netbsd", "windows":
 		return goarch == "amd64"
 	default: