[Driver] Set the feature flag library-level

Set the flag to indicate the availability of the -library-level flag in
the compiler and driver. As driver submissions can be delayed we are
integrating this flag late as a safety measure.

rdar://82742547

Author: xymus

lib/Option/features.json

@@ -8,6 +8,9 @@
     },
     {
       "name": "index-unit-output-path"
+    },
+    {
+      "name": "library-level"
     }
   ]
 }