Xcode sets up DYLD_INSERT_LIBRARIES to append libraries for the testing framework, apparently this breaks the background process set up which tries to append a path to an empty string resulting in an incorrect DYLD_INSERT_LIBRARIES value.
Created attachment 246930 [details]
Comment on attachment 246930 [details]
Clearing flags on attachment: 246930
Committed r180379: <http://trac.webkit.org/changeset/180379>
All reviewed patches have been landed. Closing bug.