Fix 'build.sh: command not found' when running inside container (#10)

Put the script path using both the env var, and the context value
for the "github.action_path". This should make the containers
see the script.

Reference:
actions/runner#1762 (comment)

action.yml

@@ -86,7 +86,10 @@ runs:
     - name: Add the action path to the gh paths to find scripts
       shell: bash
       run: |
+        # Both needed because they are unexpectedly different for contianers apparently:
+        # https://github.com/actions/runner/pull/1762#issuecomment-1105843659
         echo "${{ github.action_path }}" >> $GITHUB_PATH
+        echo "$GITHUB_ACTION_PATH" >> $GITHUB_PATH
 
     - name: Download cross from GitHub releases
       uses: giantswarm/[email protected]