tools/nolibc: use custom structs timespec and timeval

tools/nolibc: use custom structs timespec and timeval

A custom 'struct timespec' and 'struct timeval' will be necessary for
64-bit time types on 32-bit architectures. <linux/time.h> will define
other time-related types in terms of the custom 'struct timespec'.

Add custom struct definitions which for now mirror exactly the ones from
the UAPI headers, but provide the foundation for further changes.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20251220-nolibc-uapi-types-v3-8-c662992f75d7@weissschuh.net