[at-spi2-core] configure.ac: add AM_PROG_AR

[Mike Gorse <mgorse src gnome org>]

commit 234e965831e8f737310db18520b671ba4b7f7b66
Author: Thomas Petazzoni <thomas petazzoni free-electrons com>
Date:   Wed Jun 25 21:57:59 2014 +0200

    configure.ac: add AM_PROG_AR
    
    During an autoreconf, automake recommends:
    
    /usr/share/automake-1.14/am/ltlibrary.am: warning: 'libatspi.la': linking libtool libraries using a 
non-POSIX
    /usr/share/automake-1.14/am/ltlibrary.am: archiver requires 'AM_PROG_AR' in 'configure.ac'
    
    Signed-off-by: Thomas Petazzoni <thomas petazzoni free-electrons com>

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index cb8e89a..cdea54c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -28,6 +28,7 @@ AM_INIT_AUTOMAKE([1.9 -Wall foreign no-dist-gzip dist-xz])
 AM_SILENT_RULES([yes])
 
 AC_PROG_CC
+AM_PROG_AR
 LT_INIT([disable-static])
 PKG_PROG_PKG_CONFIG