On Fri, 14 Dec 2012, John R. Towler wrote:
The topic is uname(1) and uname (3), sysctl -a entries and their
intended semantics in the English words of the man pages.
Sorry, I could not find a concise statement of your problem or question.
I think you might be asking "how can the build system for some other software tell what version of NetBSD is running?" If you really need to know that, then I'd suggest "uname -r", sysctl kern.osrelease, or the .release field of the struct returned from the uname(3) library function; they all contain the same information.
On the other hand, if your real question is "how can the build system for some other product tell whether or not some feature is available?", then the answer depends on the feature that you want to test.
--apb (Alan Barrett)