Simplify signal function on Windows
Simplify signal function on Windows

The current implementation of `Signal::os_signal` always returns `0`
on Windows, so the debug call is pretty much just noise.

This is a prelude to a larger refactoring of our Signal-related code.

Signed-off-by: Christopher Maier <b4598f17a90ef80817bae8ad6c37249740caafb4@chef.io>

rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,rsertelon/habitat,rsertelon/habitat