modifyHash(update) {
		const outputOptions = this.outputOptions;
		const hashFunction = outputOptions.hashFunction;
		const hashDigest = outputOptions.hashDigest;
		const hashDigestLength = outputOptions.hashDigestLength;
		const hash = crypto.createHash(hashFunction);
		hash.update(this.fullHash);
		hash.update(update);
		this.fullHash = hash.digest(hashDigest);
		this.hash = this.fullHash.substr(0, hashDigestLength);
	}
sort here will bring all "falsy" values to the beginning
this is needed as the "hasRuntime()" chunks are dependent on the
hashes of the non-runtime chunks.