Force building against the SSL Stub library shipped with the
p4api distribution.
This does require this version of P4Ruby to use the 2012.1 version
of the P4API when being built. This will be the first p4api to be built
with SSL turned on (so that the p4sslstub library will be available).
To support true SSL, the developer will need to edit the library
lines. We should make this a configuration option for the build or
automatically detect the presence of the OpenSSL libraries.