build(gulp): don't exit prematurely during cleanup

Before this change we would exit while there were cleanup micro tasks scheduled for executions,
this caused tmp files to be left over and consume a lot of space.

Fixes #4441

gulpfile.js

@@ -1295,8 +1295,9 @@ process.on('SIGINT', function() {
     runSequence('cleanup.builder', function () {
       process.exit();
     });
+  } else {
+    process.exit();
   }
-  process.exit();
 });