Prepare deployment on master branch

[jdno]

We added steps to the GitHub Actions workflows in #3909 to upload the build artifacts for the master branch as well as for the stable branch. But the scripts that prepare the deploy/ directory were not set to run on master, causing the builds to fail.

[rami3l]

@jdno Just being curious: will this allow some sort of publicly available "thunk" builds? Because that will also be a good move towards better transparency if it does :)

[jdno]

Do you mean that users will be able to install builds from the master branch? We haven't thought about it yet, but I see no reason why we can't make the S3 bucket publicly available so that users can do something like RUSTUP_UPDATE_ROOT=https://builds.rustup.rs/${commit} rustup self update (or another domain)... 🤔

[rami3l]

Do you mean that users will be able to install builds from the master branch? We haven't thought about it yet, but I see no reason why we can't make the S3 bucket publicly available so that users can do something like RUSTUP_UPDATE_ROOT=https://builds.rustup.rs/${commit} rustup self update (or another domain)... 🤔

@jdno Yup! I had to provide CI uploads to users in order to know if some recent fix has worked for them or not (e.g. #3708 (comment)). This would be a nice addition if possible, and it seems that there shouldn't be introducing too much overhead for you?

Moved to #3932.