m4: Add warning when running QEMU as root

Running QEMU as root is a pretty bad idea, so try to make the
user aware of that as part of the configure summary.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

m4/virt-driver-qemu.m4

@@ -112,5 +112,10 @@ AC_DEFUN([LIBVIRT_DRIVER_RESULT_QEMU], [
 ])
 
 AC_DEFUN([LIBVIRT_RESULT_QEMU_PRIVILEGES], [
+  if test "$QEMU_USER" = "root"; then
+    LIBVIRT_RESULT([QEMU], [$QEMU_USER:$QEMU_GROUP],
+                   [!!! running QEMU as root is strongly discouraged !!!])
+  else
     LIBVIRT_RESULT([QEMU], [$QEMU_USER:$QEMU_GROUP])
+  fi
 ])