Auth/box previously switched to /, rather than
preserving the cwd. This would break relative
paths to items that would get pulled into the
namespace.
This change removes the '-.' flag, and causes
auth/box to keep the current working directory,
making it more usable for scripting.
-. decides where we chdir to before execing, we can't
sit where we are because our directory may not exist.
If not specified we go to '/'.
-s is used to source a rc script instead of execing cmd.
This is primarily to enable:
'#!/bin/auth/box -s'
Shebang line size is a bit tight(32), so we have this shorthand
to use rc along with setting up the required namespace components.
Changing the user to none doesn't do much for us
here. For kernel drivers that check the user of the
current proc we'll be none, but anything from devmnt
will still be accessed using creds from the original
attachment. Instead, running with none can be done
by chaining with auth/none:
auth/none auth/box ...
