Patch forthcoming.
Created attachment 224577 [details] the patch
Comment on attachment 224577 [details] the patch These could a single invocation as "set -ex", but I'm not sure why you're doing "set -x" in the first place. That's going to make things awfully verbose. It's also not clear why you're only updating these two phases rather than all of the script phases in JavaScriptCore.xcodeproj (and the remainder of WebKit).
Created attachment 224578 [details] the patch Using set -e only now, and using it in all JSC script phases.
Landed in http://trac.webkit.org/changeset/164348