SpiderMonkey 60
Upstream tarballs can now be used without a laundry list of patches, so build from an upstream tarball. (They are not yet publishing their tarballs though, so for now it still lives in releng.)
The bug for which -fno-schedule-insns was required on ARM, has been fixed, as well as bugs around installing headers in the correct location.
The --disable-jemalloc configure option is now required.
(Note: This is marked WIP because the GJS merge request !199 is still pending. Review is nonetheless welcome. The download location also doesn't exist yet; I uploaded the tarball but someone needs to run signal-ftp-sync.)
Edited by Philip Chimento