It is no longer possible to "bundle install" these versions:
$ bundle install
Fetching gem metadata from https://rubygems.org/.................
reline-0.1.3 requires ruby version >= 2.5, which is incompatible with the current version, ruby 2.4.9p362
* Build extensions for Ruby 2.7
* Try installing bundler 2.x
* Try bumping rake-compiler-dock
* Use standard RCD images
* Avoid 'rake cross native' with rake-compiler-dock
* Use Ruby 2.5 for building Ruby <= 2.6
* Use rake-compiler 1.1.0
* Specify target
* Don't update Ruby test image for now
* Use gnu for ruby build because strptime is provided by posix
* Move option to extconf.rb
* Remove unused code in Rakefile
* Add config files for kokoro test
* Use gnu 11
* Define _XOPEN_SOURCE
* Add gnu11 option
* Remove XOPEN
* Try base_cc_flags
* Try config_options
* Move time.h to top
* Try -D_XOPEN_SOURCE=700
* Define XOPEN_SOURCE directly
* Try extconf.rb
* Try CFLAGS
* Try ext.cross_config_options
* Make mac ruby release job fail on error
* Try again
* Try define _XOPEN_SOURCE in extconf.rb
* Try again
* Define __USE_XOPEN
* Remove 2.6.0
* No mingw
* Throw error on mingw
* Remove XOPEN_SOURCE in upb
* Add back mingw
* Remove comment
* Add ruby 2.6 gem build for linux
* Add docker hub organization
* Add ruby2.6 in cross compile targets
* Fix tests
* Check mac version
* No need to install php in preparation for mac
Joshua Haberman
Daniel Azuma
listonjesse
Masaki Hara
Rafi Kamal
Xiang Dai
Paul Yang
Feng Xiao