All,

I have bikeshedded the system mkfiles to some end.

Changes include:
/sys/src/mkfile installs the compilers first
/sys/src/mkfile supports install.cpus
adding a %.cpus metarule
preferring install.cpus over installall
removing the vestigial update rule
mkone and mkmany can install multiple man pages (change is incompatible)
mk -a install.cpus builds on a freshly nuked system (mk nuke.cpus)

There's too many changes to be properly distributed as a diff.
Instead, here's a repo and tarball.
https://git.sr.ht/~amavect/mkfilechanges
https://git.sr.ht/~amavect/mkfilechanges/archive/master.tar.gz

Thanks,
Amavect