libbsd include path issue

[Sichen Zhao]

Hi all,

I import wpa_supplicant files from FreeBSD to libbsd, and when i build, there are came out an error:

../../freebsd/contrib/wpa/src/crypto/crypto_openssl.c:12:10: fatal error: openssl/opensslv.h: No such file or directory
 #include <openssl/opensslv.h>
          ^~~~~~~~~~~~~~~~~~~~
compilation terminated.

I think maybe we need add a include header path to tell waf  that it has to move the file into another path.
But i don't know where to add it. I tried it in builder.py, but not working.

Best Regards
Sichen Zhao