Builds are faster with 64 jobs instead of 1 :)
It's mostly relevant for 'make' but we also use the -j flag
for 'configure' as it can also trigger a build for external
dependencies (like llvm for upcoming iOS Mono builds).
This can be reverted once a proper fix has been deployed in upstream
Mono. No ETA yet as we're busy and it's unlikely to happen if we don't
do it ourselves :)
Co-authored-by: Hein-Pieter van Braam-Stewart <hp@tmm.cx>