[gnome-nibbles] Nicer check for *-validate

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 4b29aa2abfde755621f232a27e9b885a8b838a70
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Wed Nov 6 18:36:32 2013 -0600

    Nicer check for *-validate

 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 2fa64e2..17804ac 100644
--- a/configure.ac
+++ b/configure.ac
@@ -71,8 +71,8 @@ PKG_CHECK_MODULES(GNOME_NIBBLES, [
   clutter-gtk-1.0 >= $CLUTTER_GTK_REQUIRED
 ])
 
-AC_PATH_PROG(APPDATA_VALIDATE, appdata-validate)
-AC_PATH_PROG(DESKTOP_FILE_VALIDATE, desktop-file-validate)
+AC_PATH_PROG([APPDATA_VALIDATE], [appdata-validate], [/bin/true])
+AC_PATH_PROG([DESKTOP_FILE_VALIDATE], [desktop-file-validate], [/bin/true])
 
 dnl ###########################################################################
 dnl Internationalization