In builds like https://ews-build.webkit.org/#/builders/14/builds/31777, I see it running `git clean -f -d` only, which is not enough to delete the WebKitBuild directory, since it's gitignore'd.
<rdar://problem/119947440>
In patch workflow we run the step UnApplyPatch which runs Tools/Scripts/clean-webkit. Whereas in PR workflow we run RevertPullRequestChanges step which run this git clean command. I wonder in PR workflow, we un-intentionally stopped doing proper clean build. Note that the same UnApplyPatch wasn't used in PR workflow for reason mentioned in https://bugs.webkit.org/show_bug.cgi?id=235825#c0 , but maybe we can have both UnApplyPatch as well as RevertPullRequestChanges step in PR workflow.
> both UnApplyPatch as well as RevertPullRequestChanges I mean both CleanWorkingDirectory and RevertPullRequestChanges steps.