BASERUBY version policy
Ruby 2.7 (MRI) requires Ruby 2.2 or later (== BASERUBY) to build from repository.
Tarball does not need any installed Ruby.
To build latest Ruby from repository, you need to build Ruby 2.2 and later from a tarball.
Can we make the BASERUBY version update policy?
ISeq#to_a (specific format) Ruby 2.2 or later is needed from Ruby 2.7.
The oldest version used by RubyCI machines was Ruby 2.2, so I determined update.
I needed to file a ticket about this version bump, sorry.