Log Message:
This is to fix PR 30267. (I have noticed same problem.)

The build needs optimization. So if CFLAGS doesn't contain at least
-O then add it. (Thank you Juan for idea.)

On the tech-pkg-ja@jp.NetBSD.org list, I was told (19 Dec 2005):

> This change can be accepted when judged only from my environment (i386),
> since the expression of "if empty(CFLAGS:M-O*)" is evaluated
> after setting of the environment variable (-O2).
> However, I do not have the positive proof whether this expression is evaluated
> after setting of the environment variable (-O2), in all environments.

So hopefully this doesn't break for anyone else.