Exit before second main with -funittest

[Brian Tiffin]

Is this good, bad or indifferent (a right left choice, first one 
doesn't matter)?

```d
module cpuiding;

/+ imports +/
import std.stdio: writeln;
import core.cpuid;

/++ start here +/
void main(string[] args) {
    writeln(args);

    writeln(processor());
    writeln(vendor());
}

/++ Self Test Once Only main +/
unittest {
    import core.stdc.stdlib: _Exit;
    main(["Hello, world"]);
    _Exit(1);
}
```

Dumb?  Breaks things in weird ways?   Do what you want locally, 
it's a preference for what you may want to do some times?  I'm 
finding it avoids a fair amount of clutter when testing main arg 
handling, but too new to know if it's against the grain of intent.

Cheers