Runtime: Add Xref options to be as strict as CI

.github/workflows/runtime.yml

@@ -69,6 +69,14 @@ jobs:
         make update
         make
 
+    - name: Prepare rebar
+      run: |
+        echo '{xref_ignores, [{eldap_filter_yecc, return_error, 2}
+                             ]}.' >>rebar.config
+        echo '{xref_checks, [deprecated_function_calls, deprecated_functions,
+              locals_not_used, undefined_function_calls, undefined_functions]}.
+              % Disabled: exports_not_used,' >>rebar.config
+
     - run: make xref
 
     - name: Test rel (rebar2)