ci: Cleanup build dirs on Azure Devops (backport: 4-0-x) (#16048)

* ci: Cleanup directories after build

* Use rm to cleanup source directory

* Update vsts.yml

* Check if files actually deleted

* Get rid of hidden files too

vsts.yml

@@ -233,6 +233,11 @@ jobs:
     condition: and(failed(), eq(variables['NOTIFY_SLACK'], '1'))
     timeoutInMinutes: 1
 
+  - bash: |
+      rm -rf ..?* .[!.]* *
+    condition: always()
+    displayName: 'Cleanup directories'
+
 - job: run_tests
   displayName: Run Tests
   dependsOn: build