Never use `__atomic_*` on macOS 10.7 and 10.8

Never use `__atomic_*` on macOS 10.7 and 10.8

macOS 10.7 and 10.8 had a bit wired clang which is detected as
`__GNUC__` which has `__ATOMIC_ACQ_REL` but it excepts one option at
`__atomic_is_lock_free` instead of 2.

This prevents OpenSSL to be compiled on such systems.

Fixes: #18055
Signed-off-by: Kirill A. Korinsky <kirill@korins.ky>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18056)