[libgnome-games-support] build: use AX_REQUIRE_DEFINED

[Michael Catanzaro <mcatanzaro src gnome org>]

commit cbceb3d32e92cdf662f54aa5dba9112e626f84dd
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Mon Aug 22 17:36:41 2016 -0500

    build: use AX_REQUIRE_DEFINED
    
    Never a bad idea

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 5fe6ae1..d21792f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,6 +31,7 @@ AM_PROG_VALAC([0.24])
 LT_PREREQ([2.2])
 LT_INIT([disable-static])
 
+AX_REQUIRE_DEFINED([PKG_CHECK_MODULES])
 PKG_CHECK_MODULES([LIBGNOME_GAMES_SUPPORT], [
   glib-2.0 >= 2.40
   gio-2.0 >= 2.40