"but I said I didn't want nas" -how does PK_OPTIONS work?

[George Michaelson <ggm%apnic.net@localhost>]

I am stuck with a build which wants to enable nas, but I said (in
mk.conf) I didn't want nas. 

the message below is revealing: it even SAYS I said I didn't want nas.
but it still makes it. 

why is it so? why are 'currently selected options' overriding what I
actually put in PKG_OPTIONS.SDL?

-george

==========================================================================
The supported build options for SDL are:

        aalib arts esound nas

The currently selected options are:

        aalib arts esound nas

You can select which build options to use by setting PKG_DEFAULT_OPTIONS
or the following variable.  Its current value is shown:

        PKG_OPTIONS.SDL = aalib arts esound

==========================================================================