vivaldi: fix Vulkan ICD discovery

Vivaldi ships its own libvulkan.so.1 which does not know about the
NixOS-specific /run/opengl-driver/share search path, preventing
Vulkan ICD discovery. This causes WebGPU's requestAdapter() to
return null.

Replace the bundled libvulkan.so.1 with a symlink to the NixOS-patched
vulkan-loader and add addDriverRunpath.driverLink/share to XDG_DATA_DIRS,
matching the approach used by google-chrome and microsoft-edge.

pkgs/by-name/vi/vivaldi/package.nix

@@ -47,6 +47,7 @@
   libdrm,
   libgbm,
   vulkan-loader,
+  addDriverRunpath,
   nss,
   nspr,
   patchelf,
@@ -208,9 +209,13 @@ stdenv.mkDerivation rec {
         "$out"/opt/vivaldi/product_logo_''${d}.png \
         "$out"/share/icons/hicolor/''${d}x''${d}/apps/vivaldi.png
     done
+    # replace bundled vulkan-loader with the NixOS-patched one to enable Vulkan ICD discovery
+    rm $out/opt/vivaldi/libvulkan.so.1
+    ln -s "${lib.getLib vulkan-loader}/lib/libvulkan.so.1" $out/opt/vivaldi/libvulkan.so.1
+
     wrapProgram "$out/bin/vivaldi" \
       --add-flags ${lib.escapeShellArg commandLineArgs} \
-      --prefix XDG_DATA_DIRS : ${gtk3}/share/gsettings-schemas/${gtk3.name}/ \
+      --prefix XDG_DATA_DIRS : "${addDriverRunpath.driverLink}/share:${gtk3}/share/gsettings-schemas/${gtk3.name}" \
       --prefix LD_LIBRARY_PATH : ${libPath} \
       --prefix PATH : ${coreutils}/bin \
       ''${qtWrapperArgs[@]}