In some build contexts, the 'DerivedSourcesDirectory' environment variable is not set. Deal with this properly in the "copyForwardingHeaders.cmd" script.
<rdar://problem/18023620>
Created attachment 236620 [details] Patch
Comment on attachment 236620 [details] Patch r=me
Created attachment 236626 [details] Patch
Committed r172609: <http://trac.webkit.org/changeset/172609>
Comment on attachment 236626 [details] Patch Clearing flag so it doesn't show up in the Review Queue.