esy build fails due to missing <package>.opam file in dune-private-libs

[purplezimmermann]

On my Windows 10, using esy 0.6.4 (in an administrator cmd shell), the following happens:

> esy build
info esy build 0.6.4 (using package.json)
info building @esy-ocaml/substs@0.0.1@d41d8cd9
info building ocaml@4.9.1000@d41d8cd9
...
...
...
info building @reason-native/console@0.0.3@d41d8cd9
error: build failed with exit code: 1
  build log:
    # esy-build-package: building: @opam/dune-private-libs@opam:2.5.1
    # esy-build-package: pwd: C:\Users\stefanz\.esy\3\b\opam__s__dune_private_libs-opam__c__2.5.1-f66a9529
    # esy-build-package: running: "dune" "build" "-p" "dune-private-libs" "-j" "4" "@install"
    Info: Creating file dune-project with this contents:
    | (lang dune 2.5)
    File "src/cache/dune", line 3, characters 14-37:
    3 |  (public_name dune-private-libs.cache)
                      ^^^^^^^^^^^^^^^^^^^^^^^
    Error: You cannot declare items to be installed without adding a
    <package>.opam file at the root of your project.
    To declare elements to be installed as part of package "dune-private-libs",
    add a "dune-private-libs.opam" file at the root of your project.
    Root of the project as discovered by dune: .
    error: command failed: "dune" "build" "-p" "dune-private-libs" "-j" "4" "@install" (exited with 1)
    esy-build-package: exiting with errors above...

  building @opam/dune-private-libs@opam:2.5.1
esy: exiting due to errors above

It's hard to find any further info on that. Is it a known issue with dune-private-libs or something higher up the dependency hierarchy?

Over at onivim the same issue popped up: onivim/oni2#1816

[EduardoRFS]

I stumble on that also, my trick as a workaround is to remove ~/.esy and run inside of git bash.