feat: add sha256 to OTP builds.txt

[gigatim]

This PR adds a sha256 to the builds.txt files for OTP.

Background

PR #34 added sha256 to the elixir builds.txt This comment called out that a separate PR should be created to do the same to the OTP builds.txt file. It appears this was never completed.

Also relates to #16

Test Disclaimer

I was not able to run it locally. Therefore the PR is provided without any testing at all.

[gigatim]

@ericmj Can I get a review on this PR? I do not have the permissions to request a reviewer in the GitHub UI.

[gigatim]

@wojtekmach do you have an ETA on when this might get merged into main/production?

[wojtekmach]

Before merging this, I think we should have a script ready that updates all existing builds.txt with the checksums. WDYT @ericmj?

These are all the files we need to update:

$ for arch in amd64 arm64; do for os in ubuntu-{20.04,22.04,24.04}; do echo https://builds.hex.pm/builds/otp/$arch/$os/builds.txt; done ; done
https://builds.hex.pm/builds/otp/amd64/ubuntu-20.04/builds.txt
https://builds.hex.pm/builds/otp/amd64/ubuntu-22.04/builds.txt
https://builds.hex.pm/builds/otp/amd64/ubuntu-24.04/builds.txt
https://builds.hex.pm/builds/otp/arm64/ubuntu-20.04/builds.txt
https://builds.hex.pm/builds/otp/arm64/ubuntu-22.04/builds.txt
https://builds.hex.pm/builds/otp/arm64/ubuntu-24.04/builds.txt

[gigatim]

Before merging this, I think we should have a script ready that updates all existing builds.txt with the checksums. WDYT

I disagree. This is adding additional meta data, which does not necessarily need to be retroactively added. I'm not opposed to having older versions updated, but I don't know that this PR should be blocked on that work.

For instance, the https://builds.hex.pm/builds/elixir/builds.txt only has this additional field on some (newer) lines.

[wojtekmach]

Thank you!