Fix shotover release process

[rukai]

Our release process is very brittle as we do not exercise it in any way during development.

cargo-dist did not exist when we first set this process up but it does now and it solves this problem by being batteries included and testing the release process during development: https://github.com/axodotdev/cargo-dist
So we should swap to it in the future.

However, for now I am just quickly fixing the bug so we can complete the half-complete release process.
There are a few issues:

• we ran cargo test - the project doesnt even support cargo test anymore, instead we rely on cargo nextest. Just delete it, no need to be testing everything at this point
• It creates a folder called shotover in the root of the repo, there is already a folder with that name in the root now. So lets instead use the directory of the script as the root to avoid the collision.

I verified these changes fix the issue by running build_release.sh on my local machine.

I removed the musl building dead code, there are better ways of achieving that these days anyway.