Fix file conflicts with libnet-devel
    
    Trying to install libnet-devel.x86_64 and libnet-devel.i686 fails with
    
      file /usr/bin/libnet-config conflicts between attempted installs of libnet-devel-1.2-2.fc34.x86_64 and libnet-devel-1.2-2.fc34.i686
    
    The file libnet-config contains for x86_64 the string 'lib64' and for
    i686 'lib' which makes the devel packages not installable at the same
    time.
    
    Running 'libnet-config --libs' returns '-L/usr/lib64 -lnet' for x86_64
    and without '64' for i686. As that is both the default location for
    libraries it can be omitted which this patch does.
    
    With this patch applied 'libnet-config --libs' returns just '-lnet'.
    
    Signed-off-by: Adrian Reber <adrian@lisas.de>