workflows/test: Add installer to PATH at first position

.gitea/workflows/test.yaml

@@ -25,5 +25,5 @@ jobs:
       - name: Run Tests
         shell: powershell
         run: |
-          $env:PATH += ";$(pwd)\Installer\Files"
+          $env:PATH = "$(pwd)\Installer\Files;" + $env:PATH
           $(& dotnet test Tests; $a=$lastexitcode) | findstr x*; exit $a