Function profile_namespace 

pub(crate) fn profile_namespace(
    profile: &str,
    profile_suffix: Option<&str>,
    variables: &BTreeMap<String, String>,
) -> String

Compute the cache namespace for a profile configuration.

Returns a hex-encoded SHA-256 hash of the profile name, optional suffix, and variable bindings. This ensures that different profile/suffix/variable combinations use isolated SQLite databases under target/compiler/, preventing cross-contamination of cached artifacts.