Portable ELF tooling (elfutils/libelf, needed by Mesa's radeonsi driver) relies
on several standard headers and functions Red Bear's relibc lacked:
- <byteswap.h>: bswap_16/32/64 (compiler builtins).
- <error.h>: GNU error()/error_at_line() (inline).
- <libintl.h>: gettext family as the identity map (catalog-less system; matches
glibc's no-catalog fallback behaviour).
- <ar.h>: Unix archive struct/magic (header-only).
- <search.h> + src/header/search: POSIX tsearch/tfind/tdelete/twalk + GNU
tdestroy, implemented as an unbalanced BST (conforming; POSIX mandates no
balancing).
- string: mempcpy (memcpy returning end) and rawmemchr (unbounded memchr).
All complete implementations, no stubs. Additive (no ABI break), so existing
sysroot binaries are unaffected.
