firefoxpwa: fix build failure with wrapper

pkgs/by-name/fi/firefoxpwa-unwrapped/package.nix

@@ -83,6 +83,11 @@ rustPlatform.buildRustPackage rec {
 
     wrapProgram $out/bin/firefoxpwa-connector \
       --prefix FFPWA_SYSDATA : "$out/share/firefoxpwa"
+
+    # Create empty `lib/firefoxpwa` directory so the Firefox wrapper won't fail
+    # trying to disable the update checks. It will try to write to
+    # `$out/lib/firefoxpwa/is-packaged-app`, which doesn't exist by default.
+    mkdir $out/lib/firefoxpwa
   '';
 
   passthru = {