$OpenBSD: patch-configure_ac,v 1.4 2021/06/14 20:20:35 naddy Exp $

With autoconf 2.69, AC_PROG_CC only enables C89.

Index: configure.ac
--- configure.ac.orig
+++ configure.ac
@@ -105,6 +105,7 @@ fi
 AM_PROG_AS
 dnl We really mean C99 here. The specific macro for that is gone.
 AC_PROG_CC
+AC_PROG_CC_C99
 AM_PROG_CC_C_O
 AC_PROG_CPP
 AC_PROG_INSTALL
