artichoke-dev binaries are codesigned on Apple platforms

[lopopolo]

As of https://github.com/artichoke/nightly/releases/tag/nightly-2022-09-05-apple-codesign-test-v9 and artichoke/nightly#88, Artichoke Ruby nightlies, which are installable as artichoke-dev in ruby-build, are shipping with Apple code signatures.

I tested locally and installation works as before. Signatures are preserved when installing from the latest nightly release.