Consider exporting dart path into environment variable

[DRSchlaubi]

It would be helpful to export the dart sdk path into a variable like DART_HOME so the actions can find it

Currently, you can use this

env:
  - DART_SDK: ${{ runner.tool_cache }}/dart-sdk/

[mit-mit]

This is now available in the main channel; @DRSchlaubi could you give uses: dart-lang/setup-dart@7e4ec4f1811e09ce8f339b4d3044220ca799e6c6 a try and let me know if that works as expected?

[mit-mit]

Tested this in https://github.com/dart-lang/setup-dart/actions/runs/1328348805

Note that on windows, you need to use bash to see the variable:

      - name: Print DART_HOME
        shell: bash
        run: echo "Dart SDK installed in $DART_HOME"

[mit-mit]

Now available in dart-lang/setup-dart@v1.3. For sample output see #45

[DRSchlaubi]

Okay thanks I'll test it

[DRSchlaubi]

Seems to work