Commit fc6aedc2 added autoconf checks for
those libraries, but the AC_CHECK_LIB macros have the side-effect of adding
-lDDBoost and -emcconnect to LIBS, which means that they will be linked in
all binaries. That's not what we want, they should only be linked into the
few binaries that actually use them.

This hopefully fixes the build failure seen on some platforms.