$OpenBSD: patch-tools_gn_args_cc,v 1.4 2017/03/14 12:18:54 robert Exp $
--- tools/gn/args.cc.orig.port	Thu Mar  9 21:04:48 2017
+++ tools/gn/args.cc	Fri Mar 10 07:46:25 2017
@@ -274,6 +274,8 @@ void Args::SetSystemVarsLocked(Scope* dest) const {
   os = "android";
 #elif defined(OS_NETBSD)
   os = "netbsd";
+#elif defined(OS_OPENBSD)
+  os = "openbsd";
 #else
   #error Unknown OS type.
 #endif
