For some reason, the build system enables NEON on platforms
that is should not. Fixes compilation on several ARM targets.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Botan (Japanese for peony) is a cryptography library written in C++11
and released under the permissive Simplified BSD license.

Botan's goal is to be the best option for cryptography in new C++ code
by offering the tools necessary to implement a range of practical
systems, such as TLS/DTLS, PKIX certificate handling, PKCS#11 and TPM
hardware support, password hashing, and post quantum crypto schemes. In
addition to the C++, botan has a C89 API specifically designed to be
easy to call from other languages. A Python binding using ctypes calling
the C89 API is included.

github: https://github.com/randombit/botan

Signed-off-by: BangLang Huang <banglang.huang@foxmail.com>