Merge "Improve the error when srcs field has the wrong type." am: 309a1acb

			value = value.Elem()

		}

		if value.Kind() != reflect.String {

			panic(fmt.Errorf("prebuilt src field %q should be a string or a pointer to one but was %d %q", srcPropertyName, value.Kind(), value))

			panic(fmt.Errorf("prebuilt src field %q in %T in module %s should be a string or a pointer to one but was %v", srcField, srcProps, module, value))

		}

		src := value.String()

		if src == "" {