* configure.ac: Add detection for header 'sys/sysctl.h' and system
function 'sysctlbyname'.
* src/hwf-arm.c (HAS_APPLE_SYSCTLBYNAME)
(detect_arm_apple_sysctlbyname): New.
(detect_arm_hwf_by_toolchain) [__ARM_FEATURE_CRYPTO]: Also check for
ENABLE_ARM_CRYPTO_SUPPORT.
(_gcry_hwf_detect_arm) [HAS_APPLE_SYSCTLBYNAME]: Check HWFs with
'detect_arm_apple_sysctlbyname' function.