https://github.com/ruby/open3/commit/38904e204d

This allows the wrapper functions in the main open3 to be defined
while using our ProcessBuilder logic for the internal popen
implementation.

Note this adds logic to reject redirects from a numeric fd to a
live IO object (or not a String or to_path object) since we cannot
support direct IO redirects with ProcesBuilder.

This patch allows tests to complete with the ProcessBuilder impl.
Only three tests fail:

* test_numeric_file_descriptor2 and test_numeric_file_descriptor2
  fail due to redirecting streams to a pipe IO.
* test_pid fails expecting a real PID which we cannot provide via
  ProcessBuilder.

https://github.com/ruby/open3/commit/73f986c233

This adds JRuby's logic used on platforms where we do not have
native access to posix_spawn and related posix functions needed
to do fully-native subprocess launching and management. The code
here instead uses the JDK ProcessBuilder logic to simulate most
of the Open3 functionality.

This code does not pass all tests, currently, but provides most of
the key functionality on pure-Java (i.e. no native FFI) platforms.

https://github.com/ruby/open3/commit/689da19c42

"requiring version.rb" strategy has some issues.

- cannot work when cross-compiling
- often introduces wrong namespace
- must know the superclasses
- costs at each runtime than at build-time

etc.

https://github.com/ruby/actions/runs/500526558?check_suite_focus=true#step:16:127
```
Failures:

  1) Bundler.setup when Bundler is bundled doesn't blow up
     Failure/Error: expect(err).to be_empty

       expected `"fatal: not a git repository (or any of the parent directories): .git\nfatal: not a git repository (o...the parent directories): .git\nfatal: not a git repository (or any of the parent directories): .git".empty?` to return true, got false

       Commands:
       $ /home/runner/work/actions/actions/snapshot-master/ruby \
         -I/home/runner/work/actions/actions/snapshot-master/lib:/home/runner/work/actions/actions/snapshot-master/spec/bundler \
         -rsupport/hax -rsupport/artifice/fail \
         /home/runner/work/actions/actions/snapshot-master/libexec/bundle install --retry 0
       Resolving dependencies...
       Using bundler 2.1.4
       Bundle complete! 1 Gemfile dependency, 1 gem now installed.
       Use `bundle info [gemname]` to see where a bundled gem is installed.
       fatal: not a git repository (or any of the parent directories): .git
       fatal: not a git repository (or any of the parent directories): .git
       fatal: not a git repository (or any of the parent directories): .git
       # $? => 0

       $ /home/runner/work/actions/actions/snapshot-master/ruby \
         -I/home/runner/work/actions/actions/snapshot-master/lib:/home/runner/work/actions/actions/snapshot-master/spec/bundler \
         -rsupport/hax -rsupport/artifice/fail \
         /home/runner/work/actions/actions/snapshot-master/libexec/bundle exec ruby -e \
         require\ \'bundler\'\;\ Bundler.setup
       fatal: not a git repository (or any of the parent directories): .git
       fatal: not a git repository (or any of the parent directories): .git
       fatal: not a git repository (or any of the parent directories): .git
       # $? => 0
     # ./spec/bundler/runtime/setup_spec.rb:1056:in `block (3 levels) in <top (required)>'
     # ./spec/bundler/spec_helper.rb:111:in `block (3 levels) in <top (required)>'
     # ./spec/bundler/spec_helper.rb:111:in `block (2 levels) in <top (required)>'
     # ./spec/bundler/spec_helper.rb:78:in `block (2 levels) in <top (required)>'
make: *** [yes-test-bundler] Error 1
```