build: fix hardcoded android ABI

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
build: export HAVE_64

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
build: add arm64-v8a support

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>