tee: tune when later -p overrides earlier

tee: tune when later -p overrides earlier

* src/tee.c (pipe_check): Make this a local var instead
of a static var.  This suppresses a -Wmaybe-uninitialized
diagnostic with gcc 12.2.1 20221121 (Red Hat 12.2.1-4).
(main): Don’t set pipe_check unnecessarily if a later
-p option overrides an earlier one that wants pipe_check.
Problem discovered when I investigated the GCC warning.