The current IFUNC selection is always using the most recent
features which are available via AT_HWCAP. But in
some scenarios it is useful to adjust this selection.
The environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....
can be used to enable HWCAP feature yyy, disable HWCAP feature xxx,
where the feature name is case-sensitive and has to match the ones
used in sysdeps/loongarch/cpu-tunables.c.
Signed-off-by: caiyinyu <caiyinyu@loongson.cn>
