Remove libunwind from dependencies
    
    In the case where a C application uses zeromq and then dlopen's a C++
    module, the C++ exception handling functionality will not work because
    libzmg pulls in libunwind. Then the C++ module brings in libstdc++ and
    libgcc_s, the personality function which is part of the C++ exception
    handling the runtime finds the version of
    _Unwind_GetLanguageSpecificData which is in libunwind rather than the
    one that is in libgcc_s and uses that. However, version does not have
    a complete implementation and so it fails causing the application to
    abort. This fixes https://bugzilla.redhat.com/show_bug.cgi?id=2175966
    
    Signed-off-by: Ben Woodard <woodard@redhat.com>