cachix fails to upload musl artifacts in github actions on macos

[cpcloud]

Here's a CI run demonstrating the issue.

It looks like cachix can't read symlinks produced by the (successful) build. This only happens on macos and only when building musl artifacts.

https://github.com/cpcloud/protoletariat/runs/4576549612?check_suite_focus=true

[cpcloud]

Another interesting bit of information is that it seems to be even more narrow: only the ld artifact from the build is failing to upload. Other musl artifacts upload just fine. E.g., https://github.com/cpcloud/protoletariat/runs/4576549477?check_suite_focus=true

[domenkozar]

This is going to be fixed in Cachix 1.7, due to release tomorrow.