makefiles: Split AR into AR and ARFLAGS.
diff --git a/configure.ac b/configure.ac
index 5d06e6f..b23a586 100644
--- a/configure.ac
+++ b/configure.ac
@@ -158,6 +158,7 @@
 AC_CHECK_TOOLS(AS,[gas as],as)
 AC_CHECK_TOOL(LD,ld,ld)
 AC_CHECK_TOOL(AR,ar,ar)
+AC_SUBST(ARFLAGS,rc)
 AC_PROG_RANLIB
 AC_CHECK_TOOL(STRIP,strip,strip)
 AC_CHECK_TOOL(WINDRES,windres,false)