This is just a random example picked from recent source changes, I bet there
are other example out there (I just didn't bother to search for them):

---8<---
Date: Thu,  6 Jun 2002 11:09:08 +0300 (EEST)
From: grant beattie <grant@netbsd.org>  
To: pkgsrc-changes@netbsd.org
Subject: CVS commit: pkgsrc/emulators/bochs
Message-Id: <20020606080908.84CC7B004@cvs.netbsd.org>

Module Name:    pkgsrc
Committed By:   grant
Date:           Thu Jun  6 08:09:08 UTC 2002

Modified Files:
        pkgsrc/emulators/bochs: Makefile

Log Message:
add CXXFLAGS=-O2
reported by Wojciech Puchar <wojtek@3miasto.net> in pkg/17181.
--->8---

I wonder if hardcoding -O2 here is a good idea.
Wouldn't it be better to use the arch specific default setting from sys.mk?

Martin