Determine whether ld causes an error for a missing file
Ld-missing-input-ok is an ld special (see ld).
The accessor is (ld-missing-input-ok state) and the updater is
(set-ld-missing-input-ok val state). The value of
ld-missing-input-ok must be either nil, t, or :warn. The
initial value of ld-missing-input-ok is nil.
The general-purpose ACL2 read-eval-print loop, ld, is controlled by
various flags that control its behavior, and ld-missing-input-ok is one
of them. In brief, the first argument of ld can indicate a file from
which to read input. If the file does not exist, it is an error by default,
but ld becomes essentially a no-op if t or :warn is supplied
for :ld-missing-input-ok, where :warn prints a warning. Also see