Don't link distributions against itself.

DISTRIBUTIONS_SHARED_LIBS was used for two things: the libraries to link
to libdistributions, and the libraries to link to programs using
libdistributions. Now it is only the libraries to link to
libdistributions; programs using libdistributions link to
libdistributions and get its dependencies automatically.
Merge pull request #81 from forcedotcom/fix-recursive-link

Don't link distributions against itself.