fix(package): ensure electron-packager throws if fails

[erickzhao]

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Summarize your changes:

Fixes #3128

For context, we use some pretty ugly hacks for Electron Packager to work with Listr2 (without being written with Listr2 itself).

To make this work, there's a single packagerPromise resolving from the electron-packager call:

forge/packages/api/core/src/api/package.ts

Lines 307 to 313 in 6a118c6

	ctx.packagerPromise = packager(packageOpts);
	// Handle error by failing this task
	// rejects is populated by the reject handlers for every
	// signal based promise in every subtask
	ctx.packagerPromise.catch((err) => {
	for (const reject of rejects) reject(err);
	});

If this Promise rejects, then we catch it and reject it with an array of reject handlers from all subtasks declared above:

forge/packages/api/core/src/api/package.ts

Line 177 in 6a118c6

const rejects: ((err: any) => void)[] = [];

The problem here is that the rejects array is empty in the first .catch(), so the error is caught but never propagated. Therefore, the CLI ends up stalling indefinitely.

To solve this problem, we add the Promise reject handler from targetsPromise to the rejects array so the packagerPromise catch clause has a valid rejects target.

const targetsPromise = new Promise<InternalTargetDefinition[]>((resolve, reject) => {
  provideTargets = resolve;
  rejects.push(reject);
});