Fix Bundler cache when there is no Gemfile.lock

• Fixes #105
• Also include the OS version in the cache key for Windows and macOS.

Always use Bundler 1 for JRuby 9.1.x

• Fixes #108

Use a hardcoded toolcache path since we need to extract there to let Ruby work

• Fixes #104 and #106.

truffleruby-head now ships with Bundler 2

v1.50.1

Bundler 2 is shipped with truffleruby-head now

Use the new builds under the hostedtoolcache

• See #98.
• Add support for Ruby 3.0.0-preview1 #100.
• Fix OpenSSL version used on macOS #97.

Remove Rubinius support

• Fixes #101.

Deprecate Rubinius builds

See #101.

Add Ruby 2.7.2

• Fixes #93.

Bump @actions/core from 1.2.4 to 1.2.6

Bumps [@actions/core](https://github.com/actions/toolkit/tree/HEAD/packages/core) from 1.2.4 to 1.2.6.
- [Release notes](https://github.com/actions/toolkit/releases)
- [Changelog](https://github.com/actions/toolkit/blob/main/packages/core/RELEASES.md)
- [Commits](https://github.com/actions/toolkit/commits/HEAD/packages/core)

Signed-off-by: dependabot[bot] <support@github.com>

Add support for gems.rb/gems.locked

• #84