Don't build AFALG on android

This didn't get built anyway for gcc because it was detected as a cross
compile. But it did get built for clang - even though this is still a cross
compile build. This disables it in all cases for Android.

Fixes #5748

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/6057)