Bug 1626555 - Add `dom/res` to the list of non-unified-build-compatible directories. r=sg

Depends on D96398

Differential Revision: https://phabricator.services.mozilla.com/D96399

build/non-unified-compat

@@ -49,4 +49,5 @@ dom/plugins/
 dom/power/
 dom/quota/
 dom/reporting/
+dom/res/
 dom/simpledb/