Add Ruby 3.4 as a supported version

[stanhu]

Also test Ruby 3.4.x in CI.

[stanhu]

It seems https://github.com/oxidize-rb/rb-sys/pull/472/files already handles this, so I'll pull this commit.

[ianks]

thank you!

[stanhu]

@ianks Thanks for the quick merge! I'm having trouble using ruby_gte_3_4 in my Ruby 3.4.1 app even after updating to v0.9.105. RB_SYS_ENV_DEBUG=1 cargo build shows that the 3_4 defintions are there:

  cargo:rustc-check-cfg=cfg(ruby_version_lt_3_4)
  cargo:rustc-check-cfg=cfg(ruby_version_gt_3_4)
  cargo:rustc-check-cfg=cfg(ruby_version_gte_3_4)
  cargo:rustc-check-cfg=cfg(ruby_version_eq_3_4)
  cargo:rustc-check-cfg=cfg(ruby_version_lte_3_4)
  cargo:rustc-check-cfg=cfg(ruby_3_4)
  cargo:rustc-cfg=ruby_3_4
  cargo:rustc-check-cfg=cfg(ruby_3_4_1)
  cargo:rustc-cfg=ruby_3_4_1

Does rb-sys-env also need to be updated?

UPDATE: The compile works if I point to main:

[build-dependencies]
rb-sys-env = { git = "https://github.com/oxidize-rb/rb-sys.git", branch = "main" }

[ianks]

I pushed a new version of rb-sys-env recently, it should have these changes: https://crates.io/crates/rb-sys-env/0.2.2