Problem: ocamlformat is configured to format files in-place and thus go
via creating a temporary file for that. Because temporary file resides
in a different directory ocamlformat can't find `.ocamlformat`
configuration files in an original location of source files.
Solution: ocamlformat since version 0.8 can read sources on stdin and
spur result on stdout. We reconfigure ocamlformat to use a simpler
interface.
