Ruby: Install rustc to enable yjit

[runephilosof-abtion]

Ruby 3.2 will install with yjit enabled when rustc is installed.

[samruddhikhandale]

Hi 👋

I understand that rustc is the Rust compiler which is needed to compile the Rust parts of YJIT. If rustc is installed on your system, Ruby 3.2 will be installed with YJIT enabled. If rustc is not installed, Ruby 3.2 will still install, but YJIT will be disabled.

As YJIT is still experimental, I'd hold off from adding rustc until we hear more requests for the same.
Let's keep this PR open for gathering more community feedback. Thanks!

[andrewn617]

Hi @samruddhikhandale I saw this issue an wanted to clarify a couple things.

YJIT is no longer experimental. In Rails 7.2, when running ruby 3.3, YJIT is enabled by default.

It's not exactly right to say that YJIT will be disabled when rustc is not installed - YJIT will not be installed at all, so it cannot be enabled. With rustc installed, it will give user the option to use YJIT if they choose (or if it is enabled by default for their rails/ruby version). So IMO it would be better to have rustc installed always, otherwise the user cannot benefit from yjit.

[eitsupi]

Just a question: I am not familiar with the Ruby source code, but I wonder if installing Rust in the OS package manager is really desirable here.
I mean, is Ruby's MSRV small enough and is a few years old Rustc like Debian stable provides enough?

If not, then perhaps we need to use rustup and configure it to install the latest rustc.