ash: return exit status of nofork applets (again)

ash: return exit status of nofork applets (again)

Since commit d81af7216 (ash: eval: Reap zombies after built-in commands
and functions) if the shell is compiled with SH_STANDALONE and SH_NOFORK
enabled nofork applets potentially return the incorrect status.

The status value returned by evalcommand() in this case is obtained from
exitstatus in a call to waitforjob(NULL).  This overwrites the status
set for nonfork applets.

If this commit seems familiar it's essentially a reversion of commit
5ccb0e92fa (ash: return exit status of nofork applets).  What was correct
in 2016 is wrong in 2020 and vice versa.

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>