Add ASAN flag to compiler when preprocessing sandboxes which will make sure ASAN_ENABLED is set.
<rdar://problem/117038358>
Pull request: https://github.com/WebKit/WebKit/pull/19134
Committed 269417@main (65f3f986599d): <https://commits.webkit.org/269417@main> Reviewed commits have been landed. Closing PR #19134 and removing active labels.