Fix quitAndInstall not working on macOS with autoInstallOnAppQuit=false

- Would never call nativeUpdater.checkForUpdates() if not installing on
  quit. Thus neither squirrelDownloadedUpdate was true nor the
  nativeUpdater's event "update-downloaded" be emitted. Leading to
  nothing happening.

- This commit fixes it by calling the checkForUpdates() in
  MacUpdater.quitAndInstall() when necessary

Signed-off-by: Sebastian Malton <sebastian@malton.name>

packages/electron-updater/src/MacUpdater.ts

@@ -176,7 +176,15 @@ export class MacUpdater extends AppUpdater {
       // update already fetched by Squirrel, it's ready to install
       this.nativeUpdater.quitAndInstall()
     } else {
-      // quit and install as soon as Squirrel get the update
+      if (!this.autoInstallOnAppQuit) {
+        /**
+         * If this was not `true` previously then MacUpdater.doDownloadUpdate()
+         * would not actually initiate the downloading by electron's autoUpdater
+         */
+        this.nativeUpdater.checkForUpdates();
+      }
+
+      // Quit and install as soon as Squirrel get the update
       this.nativeUpdater.on("update-downloaded", () => {
         this.nativeUpdater.quitAndInstall()
       })