auto: Check for help2man/gengetopt, and bail out if not found.
auto: Check for help2man/gengetopt, and bail out if not found.

Both are required to build.

While here, if `--enable-tests` passed, check for `check` and
if not found, bail out as well.

Yubico/libu2f-server,Yubico/libu2f-server