build: drop files generated by config.status from tarball

The rule of thumb is that any file generated by config.status
is a) reproducible by any user, b) dependent on configure options.
Therefore, it is inappropriate to include such generated files
in the tarball (for proof, Makefile is generated from Makefile.in;
the former is not in the tarball while the latter is).

* Makefile.am (EXTRA_DIST): Remove files covered by AC_OUTPUT.

Makefile.am

@@ -16,9 +16,9 @@ XML_EXAMPLES = \
 
 EXTRA_DIST = \
   ChangeLog-old \
-  libvirt.spec libvirt.spec.in \
+  libvirt.spec.in \
   mingw32-libvirt.spec.in \
-  libvirt.pc libvirt.pc.in \
+  libvirt.pc.in \
   autobuild.sh \
   Makefile.nonreentrant \
   autogen.sh \