virt-driver-qemu.m4: Require YAJL

There is no way that qemu driver can work without being able to
format/parse JSON.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

m4/virt-driver-qemu.m4

@@ -26,6 +26,15 @@ AC_DEFUN([LIBVIRT_DRIVER_ARG_QEMU], [
 ])
 
 AC_DEFUN([LIBVIRT_DRIVER_CHECK_QEMU], [
+  dnl There is no way qemu driver will work without JSON support
+  AC_REQUIRE([LIBVIRT_CHECK_YAJL])
+  if test "$with_qemu:$with_yajl" = "yes:no"; then
+    AC_MSG_ERROR([YAJL or YAJL2 is required to build QEMU driver])
+  fi
+  if test "$with_qemu" = "check"; then
+    with_qemu=$with_yajl
+  fi
+
   if test "$with_qemu" = "yes" ; then
     AC_DEFINE_UNQUOTED([WITH_QEMU], 1, [whether QEMU driver is enabled])
   fi