havoc: fix cross

Uses literal "pkg-config" rather than $PKG_CONFIG, but that's fine,
because the only thing it uses for is wayland-protocols, which is
architecture-independent, so we just move it into nativeBuildInputs
and get pkg-config from pkgsBuildBuild.

pkgs/applications/terminal-emulators/havoc/default.nix

@@ -3,8 +3,9 @@
 , fetchFromGitHub
 , libxkbcommon
 , pkg-config
-, wayland
 , wayland-protocols
+, wayland-scanner
+, wayland
 }:
 
 stdenv.mkDerivation rec {
@@ -18,14 +19,18 @@ stdenv.mkDerivation rec {
     hash = "sha256-jvGm2gFdMS61otETF7gOEpYn6IuLfqI95IpEVfIv+C4=";
   };
 
-  nativeBuildInputs = [
+  depsBuildBuild = [
     pkg-config
   ];
 
+  nativeBuildInputs = [
+    wayland-protocols
+    wayland-scanner
+  ];
+
   buildInputs = [
     libxkbcommon
     wayland
-    wayland-protocols
   ];
 
   dontConfigure = true;