Function cargo::core::summary::build_feature_map

fn build_feature_map(
    pkg_id: PackageId,
    features: &BTreeMap<InternedString, Vec<InternedString>>,
    dependencies: &[Dependency]
) -> CargoResult<FeatureMap>

Checks features for errors, bailing out a CargoResult:Err if invalid, and creates FeatureValues for each feature.