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

android/variable_test.go

@@ -112,6 +112,7 @@ var printfIntoPropertyTestCases = []printfIntoPropertyTestCase{
 }
 
 func TestPrintfIntoProperty(t *testing.T) {
+	t.Parallel()
 	for _, testCase := range printfIntoPropertyTestCases {
 		s := testCase.in
 		v := reflect.ValueOf(&s).Elem()
@@ -157,6 +158,7 @@ func testProductVariableModuleFactoryFactory(props interface{}) func() Module {
 }
 
 func TestProductVariables(t *testing.T) {
+	t.Parallel()
 	ctx := NewTestContext()
 	// A module type that has a srcs property but not a cflags property.
 	ctx.RegisterModuleType("module1", testProductVariableModuleFactoryFactory(&struct {
@@ -265,6 +267,7 @@ func productVariablesDefaultsTestDefaultsFactory() Module {
 
 // Test a defaults module that supports more product variable properties than the target module.
 func TestProductVariablesDefaults(t *testing.T) {
+	t.Parallel()
 	bp := `
 		defaults {
 			name: "defaults",