 - Package and (optionally) use libnbd
 - Use fix for --no-git bootstrap fix when it lands upstream, and drop
   the patch
 - See if we can use non-bundled Jitter
 - Still getting 'bison -y' issues

Build failures:
 - Debian:
     ./configure[6522]: syntax error: unexpected 'ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c89'
 - NetBSD 9
     https://mail.gnu.org/archive/html/poke-devel/2020-11/msg00159.html
 - OpenBSD (transient)
 - OpenIndiana Hipster (transient)
 - 'unknown instruction' on macOS:
     https://mail.gnu.org/archive/html/poke-devel/2020-11/msg00160.html

Runtime issues:
 - Ubuntu 16.04: multi-minute hangs printing welcome message
    - https://mail.gnu.org/archive/html/poke-devel/2020-11/msg00158.html
    - try CONFIGURE_FLAGS+= --without-hserver

To test:
 - FreeBSD 12
