improve GOOS=tamago test coverage

Author: abarisani

src/cmd/dist/test.go

@@ -887,7 +887,7 @@ func (t *tester) registerTests() {
 		t.registerRaceTests()
 	}
 
-	if goos != "android" && !t.iOS() {
+	if goos != "android" && !t.iOS() && goos != "tamago" {
 		// Only start multiple test dir shards on builders,
 		// where they get distributed to multiple machines.
 		// See issues 20141 and 31834.

src/cmd/internal/testdir/testdir_test.go

@@ -116,10 +116,6 @@ func Test(t *testing.T) {
 	goExperiment = env.GOEXPERIMENT
 	goDebug = env.GODEBUG
 
-	if goos == "tamago" {
-		t.Skipf("skipping: unsupported")
-	}
-
 	common := testCommon{
 		gorootTestDir: filepath.Join(testenv.GOROOT(t), "test"),
 		runoutputGate: make(chan bool, *runoutputLimit),