cmd/dist: increase timeout for standard tests

The cmd/go tests run too long on a Raspberry Pi.  I've cut times as
much as I can see without more serious steps like not running tests.

Fixes #11779.

Change-Id: Ice5da052902decea2e6ac32d0f2ce084c39ea1ab
Reviewed-on: https://go-review.googlesource.com/12368
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/dist/test.go

@@ -259,7 +259,7 @@ func (t *tester) registerStdTest(pkg string) {
 				"test",
 				"-short",
 				t.tags(),
-				t.timeout(120),
+				t.timeout(180),
 				"-gcflags=" + os.Getenv("GO_GCFLAGS"),
 			}
 			if t.race {