openssl: fix compilation for i386

Closes #3445.

OpenSSL emits bswap instructions when building for i386 targets which
unfortunately is only available on 486+ class processors.
Since the normal workaround is detected at build time and we are cross
compiling we need to specify this.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>