test: fix flakes of rebuilds TS worker

Not quite sure why such a long 'debounceTime' is needed anything under `2500` is a constant failure locally and this is also rather flaky on CI when it doesn't run as the first test.

It seems that the outputted files contents don't get updated in time.

Author: alan-agius4

packages/angular_devkit/build_angular/test/browser/web-worker_spec_large.ts

@@ -138,18 +138,20 @@ describe('Browser Builder Web Worker support', () => {
       watch: true,
     };
 
-    let buildCount = 0;
     let phase = 1;
     const workerPath = join(outputPath, '0.worker.js');
     let workerContent = '';
 
     const run = await architect.scheduleTarget(target, overrides);
     await run.output.pipe(
       // Wait for files to be written to disk.
-      debounceTime(1000),
+      // FIXME: Not quite sure why such a long 'debounceTime' is needed.
+      // Anything under `2500` is a constant failure locally when using
+      // 'fdescribe' and this tests doesn't run as first one and is also rather flaky on CI.
+      // It seems that the outputted files contents don't get updated in time.
+      debounceTime(2500),
       tap((buildEvent) => expect(buildEvent.success).toBe(true, 'build should succeed')),
       tap(() => {
-        buildCount++;
         switch (phase) {
           case 1:
             // Original worker content should be there.