$NetBSD: patch-Makefile,v 1.1 2019/06/09 13:58:08 nia Exp $

Do not use -Werror or override CFLAGS.

--- Makefile.orig	2019-03-28 06:34:53.000000000 +0000
+++ Makefile
@@ -36,7 +36,7 @@ NET:=net.o
 EXE:=
 
 HAS_PROC:=$(shell if [ -d /proc ]; then /bin/echo -e -DHAS_PROC; fi)
-CFLAGS:=-std=gnu99 -Wreturn-type -Werror=return-type -Werror=implicit-function-declaration -Wno-unused-value $(HAS_PROC) -DHAVE_UNISTD_H
+CFLAGS+=-std=gnu99 -Wreturn-type -Wno-unused-value $(HAS_PROC) -DHAVE_UNISTD_H
 
 ifeq ($(OS),Darwin)
 LIBS=sdl2 glew