Support for / && \ paths

[simonsan]

Not sure if it's just me, but I don't think currently it's supported to do something like:

      - name: Clone nyan repository
        shell: msys2 {0}
        run: |
          cd ${{ runner.workspace }}\msys-deps\

nor something like:

      - name: Clone nyan repository
        run: 
          msys2do cd ${{ runner.workspace }}\msys-deps\

If there is a already a solution to this, please tell me :-/
Because right now I even need to copy scripts to msys because I cannot use the Github Workflow variables:

      - name: Copy Script to MSYS2
        shell: bash
        run: |
          cp .github/workflows-support/shrink-msys2.sh d:/a/_temp/msys/msys64/shrink-msys2.sh

Using the github variable ${{ runner.temp }} would result in d:\a\_temp\msys/msys64/shrink-msys2.sh which msys would parse to: d:a_tempmsys/msys64/shrink-msys2.sh.