[🚀 Feature]: Use Process.spawn instead of the child_process gem

[eregon]

Feature and motivation

Since selenium is Ruby 2.7+ it can use Process.spawn which exists since 2.4.
Process.spawn covers the whole API of child_process, so there is no need for that dependency and it should be fairly easy to remove it.
child_process is unfortunately not very actively maintained, and that causes issues, for instance oracle/truffleruby#1525 / enkessler/childprocess#172.

Usage example

As a result, selenium would have 1 less dependency, one less piece of highly platform-dependent code, and runs better on more platforms.

[github-actions]

@eregon, thank you for creating this issue. We will troubleshoot it as soon as we can.

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Thank you!

[eregon]

Another advantage is Process.spawn is faster than fork+exec s used by child_process, because that can use vfork() or posix_spawn for instance.

[p0deje]

Let's see how it goes, I've also added TruffleRuby to the list of Rubies for unit tests on CI 04ede9e

[eregon]

Thank you, that was fast!

I see the CI failed at https://github.com/SeleniumHQ/selenium/actions/runs/3448105944/jobs/5754819891
It seems LANG is not set or set to C, and HOME is not set either. Are those variables unset on purpose?

[p0deje]

I've fixed it in a2d7632. Those variables are unset by default by Bazel, so I had to explicitly propagate them. I suppose TruffleRuby also suffers from jruby/jruby#5661

[eregon]

Thank you, I've filed oracle/truffleruby#2784 to account for that.
I'm rather surprised Bazel changes the ENV like this, but that's how it is.

And with your change it seems like TruffleRuby passes the test suite, nice! https://github.com/SeleniumHQ/selenium/actions/runs/3460208424/jobs/5776525182