Simplify aligning/updating cross-tools to latest available patches

[pd95]

@vinriviere is doing a great work to provide the cross-tools for ubuntu using https://github.com/vinriviere/cross-mint-ubuntu.

This macOS cross-tools could somehow rely on his work, i.e. automatically fetching the latest sources and patches from his repository and adding the macOS specific patches to it.

This would allow getting rid of the website dependency we currently have in this project.

[vinriviere]

Note that this repository is experimental and might not stay like this forever.

And it still uses Travis CI: it will have to be migrated to GitHub Actions. However, this should not change its main structure.

[pd95]

As we do not have a dpkg environment on macOS, I would only use the binary files (sources and patches) available in your *-m68k-atari-mint folders to build the same package for macOS.

Checking-out the repository and finding those sources/patches is definitely easier to build and maintain than the hardcoded URLs to your website 😉.

The long term goal should be to have some automatic build scripts for the Homebrew environment (brew/tap whatever).

[pd95]

Perhaps it would be a good idea to get inspiration from https://github.com/riscv/homebrew-riscv and the related https://github.com/riscv/riscv-gnu-toolchain/