build-kernel: stash .deb + .pkg.tar.zst around the rpm run so all three survive (#26)

* build-kernel: release .rpm alongside .deb + .pkg.tar.zst

Now that ps5-linux-image's --distro all also produces an .rpm (paired
image PR), pick it up in the artifact upload, checksum list and
release files: block. Also add rpm as an explicit format choice so
someone can dispatch an rpm-only kernel build.

The sha256sum pipeline gets a 2>/dev/null so it doesn't complain
when an older ps5-linux-image checkout is used that only writes
deb + pkg.tar.zst.

* test: run on ubuntu-latest, point at paired ps5-linux-image branch, skip release on fork

* build-kernel: run --distro fedora after --distro all so .rpm ships

---------

Co-authored-by: Your Name <you@example.com>

.github/workflows/build-kernel.yml

@@ -43,6 +43,18 @@ jobs:
           bash image/build_image.sh --kernel-only \
             --distro "$FORMAT" \
             --patches-ref "$PATCHES_REF"
+          # build_image.sh's --distro all skips the rpm packager, and each
+          # kernel-build call wipes image/linux-bin/. Stash the deb + pkg.tar.zst
+          # from the "all" run before firing the rpm-producing "fedora" run,
+          # then restore so the release ships all three formats.
+          if [ "$FORMAT" = "all" ]; then
+            mkdir -p /tmp/kernel-stash
+            cp image/linux-bin/*.deb image/linux-bin/*.pkg.tar.zst /tmp/kernel-stash/
+            bash image/build_image.sh --kernel-only \
+              --distro fedora \
+              --patches-ref "$PATCHES_REF"
+            cp /tmp/kernel-stash/*.deb /tmp/kernel-stash/*.pkg.tar.zst image/linux-bin/
+          fi
 
       - name: Read kernel and patches version
         id: version