Consider making the build-time dependency on nghttp2 optional
Right now, the main branch needs nghttp2 to be available in order for
BIND 9 to build at all. Since nghttp2 is only required for
DNS-over-HTTPS (DoH) support - which we promised to backport to BIND
9.16 at some point - it looks slightly harsh to have a new, hard
requirement on another library (even if it is a rather ubiquitous and
not version-picky one), especially in light of a future BIND 9.16
backport.
We should probably discuss whether nghttp2 should be considered mandatory for:
- BIND 9.17+
- BIND 9.16
Any changes in this area should be "announced" in:
README.mdPLATFORMS.md- release notes.