[gimp] configure: use test in a portable way

[Nils Philippsen <nphilipp src gnome org>]

commit c13e73271b77ffc298815e7fee8b22d0750c689e
Author: Nils Philippsen <nils redhat com>
Date:   Tue Oct 1 12:16:43 2013 +0200

    configure: use test in a portable way

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index cf329d8..48e9c15 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1964,7 +1964,7 @@ if test "x$with_xvfb_run" != "xno"; then
     have_xvfb_run="no (not found)"
   fi
 fi
-AM_CONDITIONAL(HAVE_XVFB_RUN, test "x$have_xvfb_run" == "xyes")
+AM_CONDITIONAL(HAVE_XVFB_RUN, test "x$have_xvfb_run" = "xyes")
 
 
 ######################################