lvgui: Provide customized libxkbcommon

overlay/mruby-builder/mrbgems/mruby-lvgui/lvgui.nix

@@ -21,6 +21,43 @@ let
       pkgs.buildPackages.python3
     ];
   });
+  libxkbcommon = pkgs.callPackage (
+    { stdenv                                             
+    , libxkbcommon                             
+    , meson             
+    , ninja                                         
+    , pkgconfig               
+    , yacc                              
+    }:                            
+
+    libxkbcommon.overrideAttrs({...}: {
+      nativeBuildInputs = [ meson ninja pkgconfig yacc ];
+      buildInputs = [ ];                                     
+
+      mesonFlags = [   
+        "-Denable-wayland=false"
+        "-Denable-x11=false"             
+        "-Denable-docs=false"            
+
+        # This is because we're forcing uses of this build
+        # to define config and locale root; for stage-1 use.
+        # In stage-2, use the regular xkbcommon lib.
+        "-Dxkb-config-root=/NEEDS/OVERRIDE/etc/X11/xkb"
+        "-Dx-locale-root=/NEEDS/OVERRIDE/share/X11/locale"
+      ];
+
+      outputs = [ "out" "dev" ];
+
+      # Ensures we don't get any stray dependencies.
+      allowedReferences = [
+        "out"
+        "dev"
+        stdenv.cc.libc_lib
+      ];
+    })
+
+  ) {};
+
 in
   stdenv.mkDerivation {
     pname = "lvgui";
@@ -46,6 +83,7 @@ in
 
     buildInputs = [
       libevdev
+      libxkbcommon
     ]
     ++ optionals withSimulator simulatorDeps
     ;