Homebrew formula broken since 0.8.10

## Description

We maintain a custom Homebrew formula to build Solidity on macOS: [`solidity.rb`](https://github.com/ethereum/homebrew-ethereum/blob/master/solidity.rb). Since at least 0.8.10 we've been having various build issues in CI so the formula does not pass tests. It may or may not be broken on real systems. Solving these requires some debugging, preferably by someone with a mac.

Fixing this is not urgent since this affects only 0.8.x and for that version there's [an official Homebrew formula](https://github.com/Homebrew/homebrew-core/blob/master/Formula/solidity.rb). It will become an issue once we release 0.9.0 and Homebrew updates to that.

## Steps to Reproduce
I recommend looking at CI output of [job 238](https://app.circleci.com/pipelines/github/ethereum/homebrew-ethereum/221/workflows/bac6bf81-3d1c-4df5-a4de-e5b4efb77392/jobs/238) from [the PR for 0.8.14](https://github.com/ethereum/homebrew-ethereum/pull/312).

For reference, older PR with failed runs (though they're no longer relevan):
- [0.8.10](https://github.com/ethereum/homebrew-ethereum/pull/307) - especially this one has some earlier discussion about the issues.
- [0.8.12](https://github.com/ethereum/homebrew-ethereum/pull/309)
- [0.8.13](https://github.com/ethereum/homebrew-ethereum/pull/311)

Start with solidity.rb and the CircleCI output for job 238 from the 0.8.14 PR. Compare the failed runs and discussion in the linked 0.8.10, 0.8.12, and 0.8.13 PRs to identify the current build issues. Done means the custom formula builds Solidity and passes its tests in CI on macOS.

Written by the indexing model from the issue text.