packaging: add pkg-config dep on kj

Since we include kj from a header, we need to add a dependency to force
downstreams to also have it as a declared dependency or at least put it
in their include dir paths.

Given kj is what it is, this is basically unavoidable that this
dependency is visible.

Change-Id: Ia89a90f10ad8b821260db0d7fdc47aebda44e66a

lix/lix-base.pc.in

@@ -3,6 +3,7 @@ libdir=@libdir@
 includedir=@includedir@
 
 Name: Lix base
-Description: Lix Package Manager (config.hh fixup)
+Description: Lix Package Manager (base include dir)
 Version: @PACKAGE_VERSION@
+Requires: kj-async
 Cflags: -I${includedir}

perl/default.nix

@@ -45,6 +45,8 @@ perl.pkgs.toPerlModule (
         boost
         perlPackages.DBI
         perlPackages.DBDSQLite
+        # for kj-async
+        nix.passthru.capnproto-nix
       ]
       ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
       ++ lib.optional stdenv.isDarwin darwin.apple_sdk.frameworks.Security;