configure.ac: remove a couple of unused items
configure.ac: remove a couple of unused items

This configure.ac is largely a copy from systemd so it included things that we
don't use locally.
- we don't use grep, awk or ln
- AC_SYS_LARGEFILE and AC_CANONICAL_HOST are unecessary
- pkg.m4 - if that's missing you don't have pkgconfig installed. stop trying
  to build things then :)

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

libratbag/libratbag,libratbag/libratbag,whot/libratbag,libratbag/libratbag,whot/libratbag,whot/libratbag