oksh-noxz [fork] Portable OpenBSD ksh, based on the Public Domain Korn Shell (pdksh).
	git clone https://noxz.tech/git/oksh-noxz.git
	oksh-noxz

commit: 842de518cb01a353af960822553918c0ada0271f
parent: 62a13d3cebc5bda51b5d78c8f41c62734b7d40eb
author: Brian Callahan <bcallah@openbsd.org>
date:   Wed, 22 Jul 2020 16:43:47 -0400

Only add -std=gnu99 if using --no-thanks.

diff --git a/configure b/configure
@@ -11,7 +11,7 @@ cat << EOF > Makefile
 # This Makefile automatically generated by configure.
 
 CC =		$cc
-CFLAGS =	$cflags -std=gnu99
+CFLAGS =	$cflags
 EOF
 
 if [ ! -z "$ldflags" ] ; then
@@ -749,6 +749,7 @@ if [ $compileonly -eq 1 ] ; then
 fi
 
 if [ $doconfigure -eq 0 ] ; then
+  cflags="$cflags -std=gnu99"
   echo "OK, I trust you."
   echo "I'll assume you have gcc/clang and little else."
   echo "Edit Makefile and pconfig.h if needed."