Avoid double stringification in pp_complement

Avoid double stringification in pp_complement

Commit 91bba347 made targets exempt from uninit warnings.  The com-
mit message only says it has something to do with fixing warnings on
bitwise ops.

Commit a1afd1046 worked around that by doing an extra stringifica-
tion before assigning to the target, to produce an uninit warning
on purpose.

As far as I can tell, the only purpose of 91bba347 was to avoid the
warning for ~undef.  (I haven’t actually tried building the commit
before that to confirm.)

In any case, the uninit warning has been long tested for and is now
expected behaviour.

Since I am about to remove the uninit warning exemption for targets,
stop relying on that.

This speed ups the code slightly, as we avoid a double string-
ification.