Function flag_to_backend_features

pub fn flag_to_backend_features<'a, const N: usize>(
    sess: &'a Session,
    diagnostics: bool,
    to_backend_features: impl Fn(&'a str) -> SmallVec<[&'a str; N]>,
    extend_backend_features: impl FnMut(&'a str, bool),
)

Translates the -Ctarget-feature flag into a backend target feature list.

to_backend_features converts a Rust feature name into a list of backend feature names; this is used for diagnostic purposes only.

extend_backend_features extends the set of backend features (assumed to be in mutable state accessible by that closure) to enable/disable the given Rust feature name.