Function extra_kconfig_hash 

pub fn extra_kconfig_hash(extra: &str) -> String

CRC32 hash (8 hex chars) of a user-supplied --extra-kconfig fragment, hashed verbatim.

Hashes raw bytes — no comment stripping, no CRLF canonicalization. Two semantically-equivalent inputs with different comments or line endings produce different hashes and therefore land at distinct cache entries — accept the disk waste in exchange for byte-deterministic cache discrimination.