Fix building with clang on ARM64/FreeBSD

From: Jussi Kivilinna <jussi.kivilinna@iki.fi>

cipher/cipher-gcm-armv8-aarch64-ce.S | 2 +-
cipher/rijndael-armv8-aarch64-ce.S | 2 +-
cipher/sha1-armv8-aarch64-ce.S | 2 +-
cipher/sha256-armv8-aarch64-ce.S | 2 +-
configure.ac | 8 ++++++--
5 files changed, 10 insertions(+), 6 deletions(-)

See T2975: building libgcrypt fails on ARM64/FreeBSD 11x STABLE