Fix electron build on arm64

Summary:
Electron-builder puts its results in a different directory, based on the architecture you build on.

While we don't have plans to release an arm64 build internally, we still need to support local builds for testing.

Without this, it fails with a rather confusing error message:

```
Script termnated. Error: spawn zip ENOENT
    at Process.ChildProcess._handle.onexit (node:internal/child_process:283:19)
    at onErrorNT (node:internal/child_process:476:16)
    at processTicksAndRejections (node:internal/process/task_queues:82:21) {
  errno: -2,
  code: 'ENOENT',
  syscall: 'spawn zip',
  path: 'zip',
  spawnargs: [ '-qyr9', '../Flipper-mac.zip', 'Flipper.app' ]
```

Reviewed By: lblasa

Differential Revision: D48517426

fbshipit-source-id: 21a133f8fce3aee0737ce5cbccc7a692a613b98e

desktop/scripts/build-release.tsx

@@ -205,9 +205,13 @@ async function buildDist(buildFolder: string) {
     if (argv['mac-dmg']) {
       targetsRaw.push(Platform.MAC.createTarget(['dmg']));
     }
+    const macPath = path.join(
+      distDir,
+      process.arch === 'arm64' ? 'mac-arm64' : 'mac',
+    );
     postBuildCallbacks.push(() =>
       spawn('zip', ['-qyr9', '../Flipper-mac.zip', 'Flipper.app'], {
-        cwd: path.join(distDir, 'mac'),
+        cwd: macPath,
         encoding: 'utf-8',
       }),
     );