regression: coq-serapi.8.13.0+0.13.1

[emillon]

Hi,
coq-serapi.8.13.0+0.13.1 does not build with dune.3.8.0~alpha3, but it does with dune.3.7.1.
See this build:

#=== ERROR while compiling coq-serapi.8.13.0+0.13.1 ===========================#
# context              2.2.0~alpha~dev | linux/x86_64 | ocaml-base-compiler.4.14.1 | file:///home/opam/opam-repository
# path                 ~/.opam/4.14/.opam-switch/build/coq-serapi.8.13.0+0.13.1
# command              ~/.opam/opam-init/hooks/sandbox.sh build dune build -p coq-serapi -j 255
# exit-code            1
# env-file             ~/.opam/log/coq-serapi-7-872efe.env
# output-file          ~/.opam/log/coq-serapi-7-872efe.out
### output ###
# Error: exception Dune_rules__coq_config.Vars.E(_)
# Raised at Dune_rules__coq_config.Vars.fail in file
#   "src/dune_rules/coq/coq_config.ml", line 35, characters 21-49
# Called from Dune_rules__coq_config.Vars.get_path in file
#   "src/dune_rules/coq/coq_config.ml" (inlined), line 44, characters 23-32
# Called from Dune_rules__coq_config.make_res in file
#   "src/dune_rules/coq/coq_config.ml", line 186, characters 25-56
# Called from Fiber__core.O.(>>|).(fun) in file "otherlibs/fiber/src/core.ml",
#   line 250, characters 36-41
# Called from Fiber__scheduler.exec in file "otherlibs/fiber/src/scheduler.ml",
#   line 73, characters 8-11
# -> required by ("<unnamed>", ())
# -> required by ("<unnamed>", ())
# -> required by ("<unnamed>", ())
# -> required by ("Super_context.all", ())
# -> required by ("toplevel", ())
# 
# I must not crash.  Uncertainty is the mind-killer. Exceptions are the
# little-death that brings total obliteration.  I will fully express my cases. 
# Execution will pass over me and through me.  And when it has gone past, I
# will unwind the stack along its path.  Where the cases are handled there will
# be nothing.  Only I will remain.

Looks like this exception is never caught, in particular.

[emillon]

I bisected that to 98de950 (#7047) as well.

[Alizter]

This is likely due to requesting a config option that doesn't exist in 8.13.

[ejgallego]

Mmm, I was under the impression we should never query coqc for OCaml projects, how is this happening?

[emillon]

main now builds correctly