cmd/dist: let misc/cgo/testshared test timeout be scaled by slow builder

The default test timeout is 10 minutes if unspecified.

The misc/cgo/testshared test didn't use t.timeout(sec), which respects
GO_TEST_TIMEOUT_SCALE, so all builders got the default 10 minute
timeout. arm5 needs more, though, so specify 10 minutes explicitly,
which will then get scaled accordingly on slower builders.

Change-Id: I19ecfdcd9c865f2b69524484415b8fbd2852718e
Reviewed-on: https://go-review.googlesource.com/84315
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Bonventre <andybons@golang.org>

src/cmd/dist/test.go

@@ -648,7 +648,7 @@ func (t *tester) registerTests() {
 			t.registerHostTest("testcshared", "../misc/cgo/testcshared", "misc/cgo/testcshared", "cshared_test.go")
 		}
 		if t.supportedBuildmode("shared") {
-			t.registerTest("testshared", "../misc/cgo/testshared", t.goTest())
+			t.registerTest("testshared", "../misc/cgo/testshared", t.goTest(), t.timeout(600))
 		}
 		if t.supportedBuildmode("plugin") {
 			t.registerTest("testplugin", "../misc/cgo/testplugin", "./test.bash")