Add --chruby option to use a Ruby managed by chruby

[k0kubun]

This is a shorthand for -e option #111, which works like:

# same as: ./run_benchmarks.rb -e "3.1.3::/opt/rubies/3.1.3/bin/ruby"
./run_benchmarks.rb --chruby 3.1.3

# same as: ./run_benchmarks.rb -e "yjit::/opt/rubies/ruby-master/bin/ruby --yjit"
./run_benchmarks.rb --chruby "yjit::ruby-master --yjit"

Similar to -e, this is the same interface as what ruby/ruby's benchmark driver has.

[maximecb]

Good idea, but should ideally provide example usage in the readme

[k0kubun]

👍 updated README as well 9fc2cd3

[noahgibbs]

Ah, this is a good fix. I had tried a similar thing with running chruby, but it's hard to get the environment right.

This won't change the gem environment, though, right? So it would only work if the Rubies are both using the same built native extensions?

[eregon]

This won't change the gem environment, though, right? So it would only work if the Rubies are both using the same built native extensions?

I wondered the same, but the script unsets GEM_HOME/GEM_PATH above so the gem homes are the default inside the Rubies prefixes (or bundle config get path if that's set).

[noahgibbs]

Ah, okay, so we're doing that anyway. Fair. Thanks!

Wait, no. Huh, okay, sounds like I need to play with this and figure out what it does. Though still, thanks! :-)

[eregon]

It's https://github.com/k0kubun/yjit-bench/blob/9fc2cd39d2ddebdb58f0ae7965530390a225cc7f/run_benchmarks.rb#L263-L267
And that's only done if it's not the first ruby in PATH, I missed that.
So then the behavior seems:

• If it's the first Ruby in PATH use GEM_HOME/GEM_PATH as set by chruby or anything else
• Otherwise use the default gem home inside the prefix

[k0kubun]

What eregon said is the intention. I've effectively been doing the same thing as --chruby with -e for a while since I merged #138, and it's been working fine.