cmd/dist: set timeout for go1 benchmark too

so that GO_TEST_TIMEOUT_SCALE can be applied too.
It's for the mips64 builder, which is so slow that the
go1 benchmark can't finish startup within 10 minutes.

Change-Id: I1b824eb0649460101b294fb442da784e872403e7
Reviewed-on: https://go-review.googlesource.com/16901Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/test.go

@@ -463,7 +463,7 @@ func (t *tester) registerTests() {
 		}
 	}
 	if t.goos != "android" && !t.iOS() {
-		t.registerTest("bench_go1", "../test/bench/go1", "go", "test")
+		t.registerTest("bench_go1", "../test/bench/go1", "go", "test", t.timeout(600))
 	}
 	if t.goos != "android" && !t.iOS() {
 		const nShards = 5