Test $GITHUB_OUTPUT env var windows compatibility

Author: firstred

.github/workflows/test.yaml

@@ -25,7 +25,7 @@ jobs:
 
             -   name: Get composer cache directory
                 id: composer-cache
-                run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+                run: echo "dir=$(composer config cache-files-dir)" >> $env:GITHUB_OUTPUT
 
             -   name: Cache composer dependencies
                 uses: actions/cache@v4