Make find more cross‐compatible

The `-flags -nohidden` check doesn’t appear to work in G·N·U Find.
Apparently `-a` and `-o` are the Posix‐correct versions of `-and` and
`-or`, even though both G·N·U and B·S·D find seem to prefer the latter.

The `-type f` check is moved to the end, as it is computationally more
expensive than `-name` and so would benefit from an early exit.