build/lib/util.ts/rewriteSourceMappingURL
export function rewriteSourceMappingURL(sourceMappingURLBase: string): NodeJS.ReadWriteStream {
	const input = es.through();

	const output = input
		.pipe(es.mapSync<VinylFile, VinylFile>(f => {
			const contents = (<Buffer>f.contents).toString('utf8');
			const str = `//# sourceMappingURL=${sourceMappingURLBase}/${path.dirname(f.relative).replace(/\\/g, '/')}/$1`;
			f.contents = Buffer.from(contents.replace(/\n\/\/# sourceMappingURL=(.*)$/gm, str));
			return f;
		}));

	return es.duplex(input, output);
}