I've tried to build Firefox on a G5 Mac. Sadly, all the versions in portage fail to build without anything really useful in the log (attached).
Created attachment 600646 [details] build.log
Created attachment 600648 [details] environment
Created attachment 600660 [details] emerge --info
what version of nodejs do you have installed?
Closing as obsolete, the version the bug was filed against was removed and necessary information are missing. If you are still experiencing this issue with >=www-client/firefox-78.3.1 or newer please file a new bug or re-open.