build:
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os:
          - ubuntu-latest
          - windows-latest

    steps:
    - uses: actions/checkout@master
    - uses: actions/setup-node@v1
      with:
        node-version: 12
    - name: Install dependencies
      run: yarn install --dev

    - name: Build binaries and upload to GitHub
      if: shell == 'bash'
      run: yarn prebuild --all -u $PREBUILD_TOKEN
      env:
        PREBUILD_TOKEN: ${{ secrets.PREBUILD_TOKEN }}
    - name: Build binaries and upload to GitHub
      if: shell == 'powershell'
      run: yarn prebuild --all -u ${env:PREBUILD_TOKEN}
      env:
        PREBUILD_TOKEN: ${{ secrets.PREBUILD_TOKEN }}

I have this job that is supposed to upload builds to GitHub releases. It runs on both Linux and Windows. As Powershell is used as a shell for Windows builds, I have to use a different syntax to read the environment variable that stores credentials to upload to GitHub. Otherwise, my Windows builds would just fail. So I tried to add conditional steps. But now GitHub doesn’t run the action at all and instead errors with:

### ERRORED 13:33:33Z

Your workflow file was invalid: The pipeline is not valid. .github/workflows/prebuild.yml (Line: 30, Col: 11): Unrecognized named-value: 'shell'. Located at position 1 within expression: shell == 'bash',.github/workflows/prebuild.yml (Line: 35, Col: 11): Unrecognized named-value: 'shell'. Located at position 1 within expression: shell == 'powershell'

What is the suggested way of running the same steps in different shells when access to environment variables is necessary?