usr.bin/getconf: add some initial tests
Items tested via this commit are:
- Some basic POSIX constants.
- Some valid programming environments with -v.
- Some invalid programming environments via -v.
NOTE: this test makes assumptions about ILP32/LP32 vs LP64 that are
currently not true on all architectures to avoid hardcoding some
architectures in the tests. I'm working on improving getconf(1) to be
more sane about handling ILP32/LP32 vs LP64. Future commits are coming
soon to address this.
MFC after: 2 weeks
Tested with: amd64, i386
Sponsored by: Dell EMC Isilon