When dune subst is called on a file larger than 16MiB, it should not crash.
See #9538.

  $ cat > create.ml << EOF
  > let () = Unix.truncate "large.dat" 0x1_00_00_00
  > EOF
  $ touch large.dat
  $ ocaml unix.cma create.ml
  $ rm create.ml

  $ cat > dune-project << EOF
  > (lang dune 1.0)
  > (name project)
  > (package
  >  (name project))
  > EOF

This test uses subst, which needs a git repository:

  $ git init
  Initialized empty Git repository in $TESTCASE_ROOT/.git/
  $ git add dune-project
  $ git add large.dat
  $ git commit -m create | tail -n 3
   2 files changed, 4 insertions(+)
   create mode 100644 dune-project
   create mode 100644 large.dat

  $ dune subst
  Warning: Ignoring large file: large.dat
  Hint: Dune has been built as a 32-bit binary so the maximum size "dune subst"
  can operate on is 16MiB.