add python setup to build-windows.yml

so that jinja2 has somewhere to install to (may be necessary in the windows runner, unclear?)

Author: ab9rf

.github/workflows/build-windows.yml

@@ -68,6 +68,8 @@ jobs:
     name: Build win64
     runs-on: windows-2022
     steps:
+      - name: Set up Python
+        uses: actions/setup-python@v5
       - name: Install build dependencies
         run: |
           choco install sccache