MFstable/10 r280340,r280341,r280356:

r280340:

MFC r279197,r279198:

r279197:

Parallelize building bootstrap-tools

Differential Revision: https://reviews.freebsd.org/D1901
Reviewed by: ian
No serious objections from: imp

r279198:

Fill in missing dependencies for dtrace related tools so the bootstrap-tools
compiles properly on older hosts

Pointyhat to: me

r280341:

Remove dependency between usr.bin/m4 and lib/libohash

libohash doesn't exist on stable/10 (only head)

Not sure why my make buildworld didn't catch any issues

This is a direct commit to stable/10 as a followup to r280340

r280356:

Defeat race with texinfo tools built with make bootstrap-tools

This is a direct commit to stable/10 because texinfo has been removed from
head