[simple-scan/gnome-3-4: 20/25] Stop configure if vala not found

[Robert Ancell <rancell src gnome org>]

commit c12b3e044eddfe2c5156db9d038f2277d3e16c8b
Author: Robert Ancell <robert ancell canonical com>
Date:   Fri Aug 29 13:59:21 2014 +1200

    Stop configure if vala not found

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index acc2c76..45f9fb9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -8,7 +8,7 @@ GNOME_MAINTAINER_MODE_DEFINES
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
 
 AC_ISC_POSIX
-AM_PROG_VALAC([0.13.0])
+AM_PROG_VALAC([0.13.0], [], [AC_MSG_ERROR([Vala compiler not found])])
 AM_PROG_CC_C_O
 AC_HEADER_STDC