ocaml 5: restrict mm releases
They rely on string assignment syntax:
#=== ERROR while compiling mm.0.5.1 ===========================================#
# context 2.2.0~alpha~dev | linux/x86_64 | ocaml-base-compiler.5.0.0 | file:///home/opam/opam-repository
# path ~/.opam/5.0/.opam-switch/build/mm.0.5.1
# command ~/.opam/opam-init/hooks/sandbox.sh build make
# exit-code 2
# env-file ~/.opam/log/mm-8-b2184d.env
# output-file ~/.opam/log/mm-8-b2184d.out
### output ###
# make -C src all
# make[1]: Entering directory '/home/opam/.opam/5.0/.opam-switch/build/mm.0.5.1/src'
# make[2]: Entering directory '/home/opam/.opam/5.0/.opam-switch/build/mm.0.5.1/src'
# ocamldep.opt synth.mli > ._bcdi/synth.di
# ocamldep.opt MIDI.mli > ._bcdi/MIDI.di
# ocamldep.opt video.mli > ._bcdi/video.di
# ocamldep.opt image.mli > ._bcdi/image.di
# ocamldep.opt audio.mli > ._bcdi/audio.di
# ocamldep.opt ringbuffer.mli > ._bcdi/ringbuffer.di
# ocamldep.opt synth.ml > ._d/synth.d
# ocamldep.opt MIDI.ml > ._d/MIDI.d
# File "MIDI.ml", line 107, characters 8-39:
# 107 | s.[0] <- coi (0x8 lsl 4 + chan);
# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# Error: Syntax error: strings are immutable, there is no assignment syntax for them.