[krb5-auth-dialog] Fail if we can't find krb5-config

[Guido Günther <guidog src gnome org>]

commit e8232134f1ced866a56270ef4dc36fe29480c97d
Author: Guido Günther <agx sigxcpu org>
Date:   Wed Jul 7 11:07:44 2010 +0200

    Fail if we can't find krb5-config

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index afe0ef2..a23b7db 100644
--- a/configure.ac
+++ b/configure.ac
@@ -74,6 +74,8 @@ if test "x$KRB5_CONFIG" != "xnone"; then
    KRB5_CFLAGS="`${KRB5_CONFIG} --cflags krb5`"
    AC_SUBST(KRB5_CFLAGS)
    AC_SUBST(KRB5_LIBS)
+else
+   AC_MSG_ERROR([krb5-config not found. You need to install a Kerberos development package])
 fi
 
 dnl Check for API differences between Heimdal and MIT Kerberos