Add BLAKE3 hashing algorithm

This uses the single-threaded C-based routines from libblake3.

This is not optimal performance-wise but should be a good starting point
for nix compatibility with BLAKE3 hashing until a more performant
implementation based on the multi-threaded BLAKE3 routines
(written in Rust) can be developed.

src/libutil/meson.build

@@ -62,6 +62,12 @@ elif host_machine.system() == 'sunos'
   deps_other += [socket, network_service_library]
 endif
 
+blake3 = dependency(
+  'libblake3',
+  version: '>= 1.5.5',
+)
+deps_private += blake3
+
 boost = dependency(
   'boost',
   modules : ['context', 'coroutine'],