CI example job fails on Windows for fork PRs

[avdv]

Failures seems to be related to missing mingw dependencies in Windows builds: tweag/rules_haskell/actions/runs/18177924495/job/51822246615?pr=2344

It is interesting that the same job succeeded for the master branch: tweag/rules_haskell/actions/runs/18191121234/job/51786238650

At the same time, my trivial change to the doc-string should not have any impact on the presence or absence of build dependencies. Though, maybe, somehow, I'm looking at the wrong error, not sure.

The error seems to be related to the remote cache. Looking at the build (https://app.buildbuddy.io/invocation/6ddd4ea4-e6fd-44da-8a6b-770de4de2a55?actionDigest=8323378385c0c4f022e58b221c52a0b7eac0af87d5a4fc965897b2895b512b71#action) it seems to have used a single cached action, which has two files available: the object file, and the dependency file (inflate.d). The dependency file includes the paths that the build is complaining about (starting with c:/_bzl/33jjwvv5/execroot/).

The dirname after _bzl is the output directory name which is computed from the location of the workspace. I just tried to reproduce it (successfully) here: https://github.com/tweag/rules_haskell/pull/2345

The difference between the CI run on master and the PRs is that the latter are created from a fork. So somehow that leads to a change of the workspace hash and a mismatch between expected include paths.

Originally posted by @avdv in https://github.com/tweag/rules_haskell/issues/2344#issuecomment-3377326422