find_path no longer searches PATH on UNIX
The change in commit b30b32a4 regressed long-standing behavior of
find_library of searching the entries in the
PATH itself in addition to reverting the derivation of prefixes from
PATH on non-Windows platforms. Ideally they should not search
PATH itself, but some of our find modules accidentally depend on this behavior. Therefore the change regressed these find modules.
We will have to restore the behavior and possibly later drop it in a compatible way using a policy.