See attached build log.
(Please do not complain about the need for looking at the build log until you can provide an easy way to open bugs with the correct data picked out of a tinderbox log. Thanks.)
Created attachment 242259 [details]
/usr/lib/icecat/icecat is a copy of xulrunner-stub, installed by net-libs/xulrunner. xulrunner respects your LDFLAGS, so rebuild xulrunner, then icecat, and you won't see the QA warning.