<http://webkit.org/b/79512>

Reviewed by Dan Bernstein.

* WebKitTestRunner/WebKitTestRunner.xcodeproj/project.pbxproj:
(Generate Derived Sources): Use xcrun to find the path to the
compiler since that works on both iOS and OS X.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108836 268f45cc-cd09-0410-ab3c-d52691b4dbfc