[libvirt] Reconfiguring doesn't trigger regeneration of libvirt.syms

[Matthias Bolte <matthias bolte googlemail com>]

Consider this sequence of commands

$ ./configure
...
$ make
...
  GEN    libvirt.syms
...
$ ./configure --with-driver-modules
...
$ make
...

libvirt.syms doesn't get regenerated but it should as it should
contain virDriverLoadModule now.

make clean after a configure run doesn't help, as make clean dosen't
remove libvirt.syms.

So either the libvirt.syms rule needs to depend on something that
triggers a regeneration of libvirt.syms after a reconfiguration or
make clean needs to remove libvirt.syms.

I'm not sure about the correct solution here. Any suggestions?

Matthias