utils/checkpackagelib/lib_mk.py: check CONF_OPTS

As already done for {FOO}_DEPENDENCIES in commit
4910a175b3f1f4b55ff257a75945d8ffb14a4ceb, check that {FOO}_CONF_OPTS are
never overridden in a conditional

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

utils/checkpackagelib/lib_mk.py

@@ -90,6 +90,7 @@ class OverriddenVariable(_CheckFunction):
         r"_SOURCE\s*=\s*",
         r"_VERSION\s*=\s*"])))
     FORBIDDEN_OVERRIDDEN = re.compile(r"^[A-Z0-9_]+({})".format("|".join([
+        r"_CONF_OPTS\s*=\s*",
         r"_DEPENDENCIES\s*=\s*"])))
 
     def before(self):