User:Sam/Drafts/Hardened toolchain

See also: User:Sam/TODO.

State of the hardened profiles in 2021:
 * Defaults to -fstack-clash-protection
 * Defaults to -z,now
 * About to add USE=cet to which, when combined with USE=hardened, builds with -fcf-protection=full by default

Future work:
 * Migrate -fstack-clash-protection into main profiles? See.
 * Migrate -z,now to main profiles?
 * Make CET on-by-default on hardened

Further-into-the-future work:
 * Move CET into main profiles, on by default