Available SDKs Should Return the Empty List if Xcode is Not Installed
<rdar://problem/112870698>
Pull request: https://github.com/WebKit/WebKit/pull/16091
Committed 266325@main (dff1c2ab2309): <https://commits.webkit.org/266325@main> Reviewed commits have been landed. Closing PR #16091 and removing active labels.