getConcatenationBailoutReason({ moduleGraph }) {
		switch (this.externalType) {
			case "amd":
			case "amd-require":
			case "umd":
			case "umd2":
			case "system":
			case "jsonp":
				return `${this.externalType} externals can't be concatenated`;
		}
		return undefined;
	}
@param {ConcatenationBailoutReasonContext} context context
@returns {string | undefined} reason why this module can't be concatenated, undefined when it can be concatenated