[java-atk-wrapper] check if AM_PROG_AR is defined

[Magdalen Berns <mberns src gnome org>]

commit c1cc147b82c0ce7692d588d85bad5a4da9f236b7
Author: Magdalen Berns <m berns thismagpie com>
Date:   Tue Dec 30 20:29:37 2014 +0000

    check if AM_PROG_AR is defined
    
    Rather than assuming AM_PROG_AR is defined it's better to check that
    it's defined first.
    
    Bug: https://bugzilla.gnome.org/show_bug.cgi?id=742126

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7e9b62c..8d61de2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5,7 +5,7 @@ AC_CONFIG_AUX_DIR(config)
 AM_INIT_AUTOMAKE([1.11 -Wall check-news -Wdeprecated-declarations])
 
 m4_pattern_allow([AM_PROG_AR])
-AM_PROG_AR
+m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
 
 # Before making a release, the LT_VERSION string should be modified.
 # The string is of the form C:R:A.