$OpenBSD: patch-tools_build_src_engine_jam_h,v 1.3 2021/02/01 12:00:51 rsadowski Exp $

Index: tools/build/src/engine/jam.h
--- tools/build/src/engine/jam.h.orig
+++ tools/build/src/engine/jam.h
@@ -321,7 +321,9 @@
 #ifdef __OpenBSD__
     #define OSMINOR "OS=OPENBSD"
     #define OS_OPENBSD
+# if !defined(unix)
     #define unix
+# endif
 #endif
 #if defined (__FreeBSD_kernel__) && !defined(__FreeBSD__)
     #define OSMINOR "OS=KFREEBSD"
