ci: use TUNA mirror for Fedora packages

.gitea/workflows/build-windows-cross-linux.yml

@@ -19,6 +19,14 @@ jobs:
       image: fedora:41
 
     steps:
+      - name: Configure Fedora TUNA mirror
+        run: |
+          set -euo pipefail
+          sed -e 's|^metalink=|#metalink=|g' \
+              -e 's|^#baseurl=http://download.example/pub/fedora/linux|baseurl=https://mirrors.tuna.tsinghua.edu.cn/fedora|g' \
+              -i /etc/yum.repos.d/fedora*.repo
+          dnf makecache --refresh -y
+
       - name: Checkout
         run: |
           set -euo pipefail