configure: Check if AM_PROG_AR is defined.

It's not defined when using old versions of automake.

diff --git a/configure.ac b/configure.ac
index a152b7bf766815c16c2174111573148aaad7fcd6..1d1747cb2e860a90cfbe31ded39cd87e2e1aaa21 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -48,7 +48,7 @@ AC_PROG_CPP
 AC_PROG_INSTALL
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
-AM_PROG_AR
+m4_ifdef([AM_PROG_AR],[AM_PROG_AR],[])
 
 AM_PROG_CC_C_O
 AM_PROG_LEX