Make lots of tests run in parallel

Putting t.Parallel() in each test makes them run in parallel.
Additional t.Parallel() could be added to each subtest, although
that requires making a local copy of the loop variable for
table driven tests.

Test: m checkbuild
Change-Id: I5d9869ead441093f4d7c5757f2447385333a95a4
diff --git a/cc/test_data_test.go b/cc/test_data_test.go
index ae59e2f..7908aa0 100644
--- a/cc/test_data_test.go
+++ b/cc/test_data_test.go
@@ -109,6 +109,7 @@
 }
 
 func TestDataTests(t *testing.T) {
+	t.Parallel()
 	buildDir, err := ioutil.TempDir("", "soong_test_test")
 	if err != nil {
 		t.Fatal(err)