Change unrecognised features to a warning, rather than error

Give a warning rather than error if an unrecognised feature is used.
This will help compatibility when new features are added.

Signed-off-by: Darryl Green <[email protected]>

Author: dgreen-arm

tools/config/__init__.py

@@ -1354,10 +1354,10 @@ def get_features(self):
         self.cumulative_overrides['features']\
             .update_target(self.target)
 
-        for feature in self.target.features:
+        for feature in list(self.target.features):
             if feature not in ALLOWED_FEATURES:
-                raise ConfigException(
-                    "Feature '%s' is not a supported feature" % feature)
+                print("[WARNING] Feature '%s' is not a supported feature" % feature)
+                self.target.features.remove(feature)
 
         return self.target.features