Fix incorrect GitHub actions path on containers (#78)

Co-authored-by: Ian Butterworth <i.r.butterworth@gmail.com>

action.yml

@@ -96,13 +96,24 @@ runs:
 
     # github and actions/cache doesn't provide a way to update a cache at a given key, so we delete any
     # that match the restore key just before saving the new cache
+
+    # Not windows
     - uses: pyTooling/Actions/with-post-step@adef08d3bdef092282614f3b683897cefae82ee3
-      if: ${{ inputs.delete-old-caches == 'true' }}
+      if: ${{ inputs.delete-old-caches == 'true' && runner.OS != 'Windows' }}
       with:
         # seems like there has to be a `main` step in this action. Could list caches for info if we wanted
         # main:  julia ${{ github.action_path }}/handle_caches.jl "${{ github.repository }}" "list"
         main: echo ""
-        post: julia ${{ github.action_path }}/handle_caches.jl "${{ github.repository }}" "rm" "${{ steps.keys.outputs.restore-key }}"
+        post: julia $GITHUB_ACTION_PATH/handle_caches.jl "${{ github.repository }}" "rm" "${{ steps.keys.outputs.restore-key }}"
+      env:
+        GH_TOKEN: ${{ inputs.token }}
+
+    # Windows (because this action uses command prompt on windows)
+    - uses: pyTooling/Actions/with-post-step@adef08d3bdef092282614f3b683897cefae82ee3
+      if: ${{ inputs.delete-old-caches == 'true' && runner.OS == 'Windows' }}
+      with:
+        main: echo ""
+        post: cd %GITHUB_ACTION_PATH% && julia handle_caches.jl "${{ github.repository }}" "rm" "${{ steps.keys.outputs.restore-key }}"
       env:
         GH_TOKEN: ${{ inputs.token }}