Avoid multiple declarations of fn in promisify

[TomAFrench]

I'm having some issues with using this package in swc-loader which stems from the below lines.

node-util/util.js

Lines 616 to 629 in a292d8a

	if (kCustomPromisifiedSymbol && original[kCustomPromisifiedSymbol]) {
	var fn = original[kCustomPromisifiedSymbol];
	if (typeof fn !== 'function') {
	throw new TypeError('The "util.promisify.custom" argument must be of type Function');
	}
	Object.defineProperty(fn, kCustomPromisifiedSymbol, {
	value: fn, enumerable: false, writable: false, configurable: true
	});
	return fn;
	}
	function fn() {
	var promiseResolve, promiseReject;
	var promise = new Promise(function (resolve, reject) {

We've got two declarations of fn here which share the same scope (despite the fact that we can only encounter one of them) and this is triggering a build error as a result.

Failing CI build demonstrating this here

As we're restricted to var in order to support ES5, I've renamed one of these instances of fn to something that seems reasonable.

[ljharb]

I’d file that bug with swc; this is perfectly valid code.

[TomAFrench]

Fair enough, thanks. 👍