[emerillon] Return a failure if vala bindings are requested and valac is not present

[Alexandre Franke <afranke src gnome org>]

commit 00466b8e07a3107b9f6f9605ca851d66f427100d
Author: Laurent Bigonville <bigon bigon be>
Date:   Tue Aug 28 19:41:10 2012 +0200

    Return a failure if vala bindings are requested and valac is not present
    
    https://bugzilla.gnome.org/show_bug.cgi?id=682888

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index b7610c4..c70eb1b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -145,7 +145,7 @@ if test "$enable_vala" = "yes"
 then
   AM_PROG_VALAC([0.8.0])
   if test x${VALAC} = x""; then
-    exit 0;
+    AC_MSG_ERROR([Vala compiler cannot be found.])
   fi
 fi