Currently build-webkit runs autogen.sh always. The makefiles that autotools generates should be smart enough to know when the originally build files have been modified and re-rerun autogen.sh. On my machine, this change reduces a null build from 60 seconds to 14 seconds.
Created attachment 60637 [details]
Comment on attachment 60637 [details]
Looks good to me!
Committed r62564: <http://trac.webkit.org/changeset/62564>