[dev.typeparams] cmd/dist: disable -G=3 on the std go tests for now

Disable -G=3 tests on the std go tests, in order to see if -G=3 is
causing the flakiness for the dev.typeparams builder, as opposed to
other changes in typeparams branch. It's possible that -G=3 is using
more CPU/RAM that causes flakiness, as opposed to more specific bugs.

Change-Id: I610bce2aabd26b2b1fddc5e63f85ffe4e958e0d8
Reviewed-on: https://go-review.googlesource.com/c/go/+/292850
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Dan Scales <danscales@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/dist/test.go

@@ -444,8 +444,12 @@ func (t *tester) registerTests() {
 			fatalf("Error running go list std cmd: %v:\n%s", err, cmd.Stderr)
 		}
 		pkgs := strings.Fields(string(all))
-		for _, pkg := range pkgs {
-			t.registerStdTest(pkg, true)
+		if false {
+			// Disable -G=3 option for standard tests for now, since
+			// they are flaky on the builder.
+			for _, pkg := range pkgs {
+				t.registerStdTest(pkg, true /* -G=3 flag */)
+			}
 		}
 		for _, pkg := range pkgs {
 			t.registerStdTest(pkg, false)