Description of problem:
(pulled from the upstream bugzilla https://bugzilla.mozilla.org/show_bug.cgi?id=686434)
The final conclusion of that bug is:
In the build stage, rpath is set in the value of LDFLAGS. So if the xulrunner has been already installed at the rpath directory, newly generated binaries search libraries located at the rpath direcroty (old ones), not newly generated ones.
Already fixed in xulrunner-7.0.1-2.