Changes

Fix INRIA CI job other-configs

fixes suggested by reviewer

Fix ocamltest criterion for using `-custom` to link test file. (#14230)

Ocamltest uses the wrong criterion when deciding whether to link the
test program with `-custom`.

Instead of looking at the libraries being linked and checking them
for dynamically-linked C code, simply check their `lib_custom` flag.

manual(etex): trim leading spaces (#14228)

Fix test-in-prefix (#14216)

Add `flexlink.exe` and `ocamllex.exe` to the list of files that do not
link with the Config module. Normally, these are symlinks to `*.byte.exe`
or `*.opt.exe` but (depending on Windows shenanigans) `configure` may
decide to use `cp` instead of `ln -s`.