[gnome-desktop] configure.ac: Use AX_IS_RELEASE

[Javier Jardón Cabezas <jjardon src gnome org>]

commit ce56a706093d91bf04a1e108284f44d5681e932f
Author: Javier Jardón <jjardon gnome org>
Date:   Sat Oct 21 01:03:57 2017 +0100

    configure.ac: Use AX_IS_RELEASE
    
    Check for the presence of a git repository to determine if compiler
    warnings should be fatal.
    
    https://wiki.gnome.org/Projects/GnomeCommon/Migration

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6949f79..d7375e4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -10,6 +10,7 @@ m4_define(gnome_version, [gnome_platform.gnome_minor.gnome_micro]m4_ifval(gnome_
 
 AC_INIT([gnome-desktop], gnome_version,
         [http://bugzilla.gnome.org/enter_bug.cgi?product=gnome-desktop])
+AX_IS_RELEASE([git-directory])
 AC_CONFIG_SRCDIR([libgnome-desktop])
 
 AM_INIT_AUTOMAKE([1.11.2 foreign no-dist-gzip dist-xz tar-ustar])