build: drop the perror gnulib module

This fixes a problem on mingw where it doesn't know how to report
certain errnos defined by POSIX, but not used on Windows. These are
not a real problem for libvirt.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

bootstrap.conf

@@ -74,7 +74,6 @@ netdb
 nonblocking
 openpty
 passfd
-perror
 physmem
 pipe-posix
 pipe2