setup-ruby: JRuby on Windows: "bundler: command not found: rake"

Actions config used:

jobs:
  build:
    name: '${{ matrix.os }}: ${{ matrix.ruby }}'
    strategy:
      fail-fast: false
      matrix:
        os: [ ubuntu-latest, windows-latest ]
        ruby: [ 2.4, 2.5, 2.6, 2.7, jruby, truffleruby ]
    runs-on: ${{ matrix.os }}
    steps:
    - uses: actions/checkout@v2
    - name: Set up Ruby ${{ matrix.ruby }}
      uses: ruby/setup-ruby@v1
      with:
        ruby-version: ${{ matrix.ruby }}
    - run: ruby -v
    - run: bundle install --jobs 4 --retry 3
    - run: bundle exec rake

Output from the bundle exec rake step

Run bundle exec rake
  bundle exec rake
  shell: C:\Program Files\PowerShell\6\pwsh.EXE -command ". '{0}'"
bundler: command not found: rake
Install missing gem executables with `bundle install`
##[error]Process completed with exit code 1.

The bundle install step before do install rake

I assume JRuby on Windows should work out-of-the-box, right? Am I doing something wrong?

I saw #12, so I checked the asciidoctor-epub3 repo, they are installing bundler themselves, maybe that makes a difference somewhere

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Status: see https://github.com/ruby/setup-ruby/issues/18#issuecomment-583856414 and below