Dealing with pkg-config detection of FreeBSD's base OpenSSL

Recently I spotted a software that uses pkg-config to find OpenSSL on the system. This way doesn't work on FreeBSD: it does have OpenSSL in base system, but it doesn't supply '*.pc' file, unfortunately. So, when configure script tries to execute pkg-config openssl it fails, obviously.

There were a number of solutions suggested for this problem on #bsdports like replacing 'pkg-config openssl' with 'pkg-config pkg-config', depending on openssl from ports etc, but the cleanest solution is to define libssl_LIBS and libssl_CFLAGS environment variables, as was suggested by bapt@. In port's Makefile it would look something like this:

USE_OPENSSL=yes
CONFIGURE_ENV+=libssl_CFLAGS="-I${OPENSSLINC}" libssl_LIBS="-L${OPENSSLLIB} -lssl"

Yes, configure will not call pkg-config if we define these 'libssl_*' variables. While it looks quite simple, this issue took surprisingly a lot time to figure everything out. :(