CI: create the bundle directory before sudo

download-deb-closure.sh runs as root, so a debs directory it creates is
root-owned and the unprivileged index step cannot write Packages into
it. Create the directory as the runner user first; the script then
chowns the .debs to match.

Author: ejohnstown

.github/workflows/ci-deps-image.yml

@@ -52,6 +52,8 @@ jobs:
 
       - name: Resolve and download the .deb closure
         run: |
+          # Created unprivileged so the later steps can write the index.
+          mkdir -p debs
           sudo bash .github/scripts/download-deb-closure.sh \
             ".github/ci-deps/packages-${{ matrix.tag }}.txt" debs