Error on duplicate resource with same disabled flag

Also realized I hadn't handled flag negation so added that as well.

Test: Automated
Bug: 329436914
Flag: EXEMPT Aconfig not supported on host tools
Change-Id: If90ae71070306f8e0c367be7e652da9c7bd0bb22
diff --git a/tools/aapt2/cmd/Util.h b/tools/aapt2/cmd/Util.h
index 6b8813b..f8e44b7 100644
--- a/tools/aapt2/cmd/Util.h
+++ b/tools/aapt2/cmd/Util.h
@@ -49,6 +49,10 @@
 
 using FeatureFlagValues = std::map<std::string, FeatureFlagProperties, std::less<>>;
 
+std::optional<FlagStatus> GetFlagStatus(const std::optional<FeatureFlagAttribute>& flag,
+                                        const FeatureFlagValues& feature_flag_values,
+                                        std::string* out_err);
+
 // Parses a configuration density (ex. hdpi, xxhdpi, 234dpi, anydpi, etc).
 // Returns Nothing and logs a human friendly error message if the string was not legal.
 std::optional<uint16_t> ParseTargetDensityParameter(android::StringPiece arg,