Created attachment 215399 [details]
patch to www/firefox/Makefile
The good news is that even without patches, Firefox now builds on powerpc64-13.
The bad news is that it does not on powerpc64-12.
The worse news is that even though the error mentioned in this patch can actually be fixed by some further work (patch on request), it is still insufficient.
That underlying failure is the following:
/usr/local/bin/ld: cannot find -lc++
and that flag is provided from somewhere deep in the Rust build glue.
IMHO this is not worth chasing down.