feat: Enable cross compilation to increase glibc compatibility

[esafak]

Why

The current build workflow only supports glibc 2.39, from ubuntu 24. This means users on older operating systems, for example, those running self-hosted Github Runners can't use rust-script.

This will

• Enable workflow_dispatch for the release workflow.
• Update conditional logic in create-release, crates, and binaries-release jobs to check for push events and tag creation only.
• Rename the binaries job to binaries-release.
• Add a new job named binaries-test that runs on workflow_dispatch to build and upload test binaries as artifacts.
• Remove the definition of the GLIBC_VERSION environment variable from .github/workflows/release.yml.
• Inline the hardcoded value 2.28 where \$ env.GLIBC_VERSION was previously used for x86_64-unknown-linux-gnu and aarch64-unknown-linux-gnu targets in both release job matrices.
• Update GLIBC version usage in matrix targets for the new binaries-test job to use the format target.2.28 for glibc-dependent builds.

Testing

I manually triggered the release workflow and downloaded the rust-script-aarch64-unknown-linux-gnu.2.28 artifact, then inspected it in nushell:

> unzip rust-script-aarch64-unknown-linux-gnu.2.28.zip
Archive:  rust-script-aarch64-unknown-linux-gnu.2.28.zip
  inflating: rust-script

> objdump -T rust-script | lines |
    where ($it =~ "GLIBC_") |
    parse --regex ".*GLIBC_(?<version>[.0-9]*).*" |
    get version | sort | uniq

╭───┬──────╮
│ 0 │ 2.17 │
│ 1 │ 2.18 │
│ 2 │ 2.25 │
│ 3 │ 2.28 │
╰───┴──────╯

The highest number determines the glibc requirement, QED.