[giggle] build: Use AX_IS_RELEASE

[Javier Jardón Cabezas <jjardon src gnome org>]

commit 606d631a5898bbe9c35b32ac421ba4478379c16a
Author: Javier Jardón <jjardon gnome org>
Date:   Fri Nov 13 14:35:52 2015 +0000

    build: Use AX_IS_RELEASE
    
    Check for the presence of a git repository to determine whether things
    like compiler warnings should be fatal.

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 40df78e..0a8f83b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -6,6 +6,8 @@ AC_INIT([Giggle],
         [giggle],
         [http://live.gnome.org/giggle])
 
+AX_IS_RELEASE([git-directory])
+
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_SRCDIR([configure.ac])
 AC_CONFIG_MACRO_DIR([m4])