random: Use getrandom only when it's appropriate.
* random/rndgetentropy.c (_gcry_rndgetentropy_gather_random) [GRND_RANDOM]: Conditionalize the use of getrandom, as it's not a portable function.
- Fixes-commit: aab1d63e4def41593312f76de016c885ffafecde
- GnuPG-bug-id: T6442
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>