[Patch] Fix build problem with system call in compile/compile.c

[Joel Brobecker]

> > Does it work to cast the result of the call to system to (void)
> > instead? In your case, I fear that you'd be exchanging one warning
> > (return value being ignored) by another (value assigned but never
> > used).
> 
> No, I tried using "(void) system (zap);" instead of "i = system (zap);"
> and I still got the warning message.

In that case, I have no objection to your patch either, provided
a small comment is added to explain why we allow ourselves to ignore
the return value (and since you'll be touching that code anyways,
I would also rename your variable to something more explicit, such
as "ignored" or "unused" for instance).

Thank you,
-- 
Joel