Run AUR validation as non-root user in CI

.github/workflows/aur-validate.yml

@@ -33,11 +33,18 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Create non-root build user
+        run: |
+          useradd -m builder
+          chown -R builder:builder "$GITHUB_WORKSPACE"
+
       - name: Validate PKGBUILD and .SRCINFO
         shell: bash
         run: |
           set -euo pipefail
-          cd "packaging/aur/${{ matrix.pkg }}"
+          su builder -c "
+            set -euo pipefail
+            cd \"$GITHUB_WORKSPACE/packaging/aur/${{ matrix.pkg }}\"
 
             makepkg --printsrcinfo > .SRCINFO.generated
             diff -u .SRCINFO .SRCINFO.generated
@@ -45,3 +52,4 @@ jobs:
 
             makepkg --verifysource --noconfirm
             namcap PKGBUILD .SRCINFO
+          "