vulkan-loader: allow validation layers to be enabled

The loader now uses XDK_DATA_DIRS to find drivers and layers.

pkgs/development/libraries/vulkan-loader/default.nix

@@ -34,6 +34,8 @@ stdenv.mkDerivation rec {
     "-DBUILD_WSI_WAYLAND_SUPPORT=ON" # XLIB/XCB supported by default
   ];
 
+  patches = [ ./use-xdg-paths.patch ];
+
   outputs = [ "out" "dev" "demos" ];
 
   preConfigure = ''
@@ -49,10 +51,10 @@ stdenv.mkDerivation rec {
     mkdir -p $out/lib $out/bin
     cp -d loader/libvulkan.so* $out/lib
     cp demos/vulkaninfo $out/bin
-    mkdir -p $out/lib $out/etc/explicit_layer.d
+    mkdir -p $out/lib $out/share/vulkan/explicit_layer.d
     cp -d layers/*.so $out/lib/
-    cp -d layers/*.json $out/etc/explicit_layer.d/
-    sed -i "s:\\./lib:$out/lib/lib:g" "$out/etc/"**/*.json
+    cp -d layers/*.json $out/share/vulkan/explicit_layer.d/
+    sed -i "s:\\./lib:$out/lib/lib:g" "$out/share/vulkan/"*/*.json
     mkdir -p $dev/include
     cp -rv ../include $dev/
     mkdir -p $demos/bin