knightos: reduce build time dependency graph

Using asciidoc-full was unnecessary to build KnightOS-related packages
since only the a2x command matters. This change makes
cross-compilation far more noticeably faster. Closure size for each
package reduced from around 7 MB to 2 MB.

pkgs/development/tools/knightos/mkrom/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, cmake, asciidoc }:
+{ lib, stdenv, fetchFromGitHub, cmake, libxslt, asciidoc }:
 
 stdenv.mkDerivation rec {
   pname = "mkrom";
@@ -11,10 +11,8 @@ stdenv.mkDerivation rec {
     sha256 = "0xgvanya40mdwy35j94j61hsp80dm5b440iphmr5ng3kjgchvpx2";
   };
 
-  nativeBuildInputs = [
-    asciidoc
-    cmake
-  ];
+  strictDeps = true;
+  nativeBuildInputs = [ asciidoc cmake libxslt.bin ];
 
   hardeningDisable = [ "format" ];