As near as I can tell this is always the same thing as --enable-debug.
Created attachment 187760 [details] Patch
Comment on attachment 187760 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=187760&action=review Ok! > ChangeLog:9 > + do anything that --enable-deubg doesn't. deubg typo here!
Committed r142634: <http://trac.webkit.org/changeset/142634>