[Toybox] Architectural issue raised by kill.c fix.

[Rob Landley]

I was going through more of  the static analysis fixes when I noticed
that kill -l won't work if killall5 isn't enabled, because most of the
command is in killall5's flag context (and flags are zeroed if the
command is switched off). Which also means kill doesn't work right when
built with scripts/single.sh.

I want to implement two macros: FLAG_x and ALWAYS_x, but that doesn't
work conceptually because if you have a flag string
"abc"USE_BLAH("de")"fg" then the values of abc change when USE_BLAH is
disabled, but aren't actually _zero_. (The FLAG_d and FLAG_e would be
zero. It adds the zero macros by doing an allyesconfig string and adding
a zero macro for every flag it hasn't already assigned a value to...))

I think what I need to be able to do is say that one command's flags are
a subset of another command's flags, so mv can build without cp.
Possibly if I use the OPTSTR_command macro in a command and then have
more stuff defined on the left edge. Not quite sure how to change the
build scripts and annotations yet...

Anyway, sorry for the slow progress, got derailed by an architectural
issue. :)

Rob