Cleanup parameters for mock libraries
    
    All the libraries use same parameters when building, why not have it in
    one place at the begining of the Makefile.
    
    This will also ensure no new mock library will have a problem with
    missing e.g. MINGW_EXTRA_LDFLAGS.
    
    Signed-off-by: Martin Kletzander <mkletzan@redhat.com>