The command to generate termcap.small doesn't use any pipes, so this
option is not needed. Using it also breaks cross-building on hosts
where /bin/sh does not support pipefail such as Linux hosts where
/bin/sh is dash.
Reviewed by: sobomax, imp
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D37865
Split out termcap.small generation into its own Makefile under
etc/termcap, so it's properly executed by the underlying command:
make 'SUBDIR_OVERRIDE=etc' everything
Reported by: gbe
MFC after: 1 month
