Add CommonOs to Config.Targets

Previously, CommonOs was not added to Config.Targets for the test which
caused AndroidMk to crash when trying to determine if a target needed
the 2ND_ prefix added to some make variables.

Bug: 245956352
Test: m nothing
Change-Id: Ia815537ee5ce8e83df9a01c57250aa888453d138

android/test_config.go

@@ -91,6 +91,9 @@ func modifyTestConfigToSupportArchMutator(testConfig Config) {
 		},
 	}
 
+	// Make the CommonOS OsType available for all products.
+	config.Targets[CommonOS] = []Target{commonTargetMap[CommonOS.Name]}
+
 	if runtime.GOOS == "darwin" {
 		config.Targets[config.BuildOS] = config.Targets[config.BuildOS][:1]
 	}