4.11.0~dev breaks use of topfind

[avsm]

When using 4.11.0~dev, trying to opam install topkg (or anything else using topfind) seems to break:

#=== ERROR while compiling topkg.1.0.1 ========================================#
# context     2.0.4 | macos/x86_64 | ocaml-variants.4.11.0+trunk | file:///Users/avsm/src/git/ocaml/opam-repository
# path        ~/.opam/devc2/.opam-switch/build/topkg.1.0.1
# command     ~/.opam/opam-init/hooks/sandbox.sh build ocaml pkg/pkg.ml build --pkg-name topkg --dev-pkg false
# exit-code   2
# env-file    ~/.opam/log/topkg-34480-60c5c2.env
# output-file ~/.opam/log/topkg-34480-60c5c2.out
### output ###
# [...]
# File "src/topkg_main.ml", line 7, characters 5-17:
# 7 | open Topkg_result
#          ^^^^^^^^^^^^
# Error: Unbound module Topkg_result
# File "src/topkg.ml", line 9, characters 8-20:
# 9 | include Topkg_result
#             ^^^^^^^^^^^^
# Error: Unbound module Topkg_result
# File "./pkg/pkg.ml", line 27, characters 5-10:
# 27 | open Topkg
#           ^^^^^
# Error: Unbound module Topkg

(I've not had a chance to bisect this further, but figured it's a serious enough regression to open up an issue early).