Jan Beich authored Dec 17, 2018 and Janne Grunau committed Dec 20, 2018

FreeBSD 11.2 added AT_HWCAP via sysctl() while 12.0 added elf_aux_info()
which requires less code to use and is cached by libc. Only support the
latter to avoid cruft to be removed after 11.* EOL on 2021-09-30.