fix sandboxing by setting zig cache

[avsm]

fixes #1

This works on macOS for me now! Trying to get a rPi binary from my mac next...

[chris-armstrong]

Thanks - this does solve the problem, but it's no longer working on Ubuntu builds because the $TMPDIR variable is not set.

I think that long term, we want to either inject or add into the build and install wrap scripts supplied by opam an exception to the default zig read/write cache directories. Another option is to redirect them in the build and install scripts if we detect the directories provided are not writeable.

I'll create an issue to track this but I think this solution is good enough to avoid issues and complications for now.

[chris-armstrong]

Thanks - this does solve the problem, but it's no longer working on Ubuntu builds because the $TMPDIR variable is not set.

I think that long term, we want to either inject or add into the build and install wrap scripts supplied by opam an exception to the default zig read/write cache directories. Another option is to redirect them in the build and install scripts if we detect the directories provided are not writeable.

I'll create an issue to track this but I think this solution is good enough to avoid issues and complications for now.