The all target should not try to build targets that are disabled by configure.
Otherwise make will try to build the programs (even if you disabled them) and
fail if libsndfile was not found.
We will need a working all target when we want to use automake for Audacity.
src/vamp-hostsdk/PluginLoader.cpp uses the dlopen function. On some platforms
you have to link against dl for this function. configure checks for dlopen
and adds -ldl to LIBS if you have to link against dl. We need to pass this
LIBS variable when linking the hostsdk library.
