Add bazzite, bazzite-deck, batocera distro support (#20)

Each distro ships with a self-contained build-rootfs.sh that the entrypoint
calls in place of distrobuilder.  This keeps upstream's distrobuilder flow
untouched for the existing distros (ubuntu/arch/cachyos/fedora/etc.) and
isolates the new distros' build logic in their own dirs.

distros/bazzite/
  build-rootfs.sh — skopeo+umoci on ghcr.io/ublue-os/bazzite:stable,
                    promote ostree /usr/etc -> /etc, install linux-ps5 RPM,
                    mask rpm-ostree services, set up grow-rootfs + DTM-TA
                    amdgpu reprobe.
  image.yaml, grow-rootfs, grow-rootfs.service

distros/bazzite-deck/
  Symlinks into distros/bazzite/ — bazzite-deck shares all build logic;
  the case branch in build-rootfs.sh dispatches via $DISTRO.

distros/batocera/
  build-rootfs.sh — download upstream batocera-x86_64-*.img.gz, mount,
                    extract /boot/batocera squashfs, swap in linux-ps5
                    kernel, patch libretroControllers.py, install first-boot
                    SHARE-partition creator (ps5-share-init).

docker/image-builder/entrypoint.sh
  - detect_kver() helper from /kernel-debs/ package filenames
  - dispatch to distros/$DISTRO/build-rootfs.sh when present (skips
    distrobuilder for that distro)
  - EFI assembly detects /boot/efi/ vs /boot/bzImage layouts so batocera
    (which mounts FAT at /boot, not /boot/efi, for batocera-part SHARE
    detection) works alongside the standard layout

build_image.sh
  - IMG_SIZE defaults: bazzite* -> 24 GB, batocera* -> 16 GB
  - FORMAT: bazzite* -> rpm (linux-ps5 RPM); batocera* stays deb

CI workflows are NOT modified — the upstream build-image.yml /
trigger-builds.yml continue to apply and will skip these distros unless
explicitly dispatched (they're not in MULTI_DISTROS).  Local builds:
  ./build_image.sh --distro bazzite
  ./build_image.sh --distro bazzite-deck
  ./build_image.sh --distro batocera

Co-authored-by: mia26MAjFm <mia26MAjFm@users.noreply.github.com>

docker/image-builder/entrypoint.sh

@@ -10,8 +10,30 @@ EFI_LABEL="boot"
 CHROOT="/build/chroot"
 IMG="/output/ps5-${DISTRO}.img"
 
+# Detect kernel version from the staged kernel package (used by bazzite +
+# batocera rootfs builders which install the linux-ps5 kernel manually).
+detect_kver() {
+    for f in /kernel-debs/linux-ps5-*.rpm /kernel-debs/linux-ps5_*.deb \
+             /kernel-debs/linux-ps5-*.pkg.tar.zst; do
+        [ -f "$f" ] || continue
+        echo "$(basename "$f")" | grep -oE '[0-9]+\.[0-9]+\.[0-9]+' | head -1
+        return 0
+    done
+}
+KVER="$(detect_kver)"
+[ -n "$KVER" ] || { echo "WARN: could not detect KVER from /kernel-debs/"; }
+export KVER
+
 if [ "$SKIP_CHROOT" = "true" ] && [ -d "$CHROOT/bin" ]; then
     echo "=== Reusing cached $DISTRO rootfs ==="
+elif [ -x "/repo/distros/${DISTRO}/build-rootfs.sh" ]; then
+    # Distros with their own build-rootfs.sh (bazzite, bazzite-deck, batocera, ...)
+    # are responsible for populating $CHROOT themselves — distrobuilder is
+    # bypassed entirely. Most often used for OCI atomic images (bazzite via
+    # skopeo+umoci) or pre-built rootfs images (batocera squashfs).
+    echo "=== Building $DISTRO rootfs via distros/${DISTRO}/build-rootfs.sh ==="
+    rm -rf "$CHROOT"/* "$CHROOT"/.[!.]* 2>/dev/null || true
+    bash "/repo/distros/${DISTRO}/build-rootfs.sh"
 else
     echo "=== Building $DISTRO rootfs ==="
     # --- Stage files for distrobuilder's copy generators ---
@@ -139,7 +161,17 @@ cp -a "$CHROOT"/* /tmp/usb_root/
 sync
 
 echo "=== Assembling boot partition ==="
-mv /tmp/usb_root/boot/efi/* /tmp/usb_efi/ 2>/dev/null || true
+# Batocera mounts the FAT32 partition at /boot (not /boot/efi) so its
+# batocera-part SHARE auto-detection works (greps /proc/mounts for /boot).
+# Detect either layout and copy from the right place.
+if [ -d /tmp/usb_root/boot/efi ] && [ -n "$(ls -A /tmp/usb_root/boot/efi 2>/dev/null)" ]; then
+    mv /tmp/usb_root/boot/efi/* /tmp/usb_efi/ 2>/dev/null || true
+elif [ -f /tmp/usb_root/boot/bzImage ]; then
+    # batocera-style: bzImage + cmdline + everything else lives directly
+    # in /boot. Move everything into the EFI partition so the PS5 loader
+    # can find bzImage/initrd.img/cmdline.txt at the FAT root.
+    mv /tmp/usb_root/boot/* /tmp/usb_efi/ 2>/dev/null || true
+fi
 CMDLINE_TEMPLATE="/repo/distros/${DISTRO}/cmdline.txt"
 [ -f "$CMDLINE_TEMPLATE" ] || CMDLINE_TEMPLATE="/repo/boot/cmdline.txt"
 sed "s|__DISTRO__|$ROOT_LABEL|" "$CMDLINE_TEMPLATE" > /tmp/usb_efi/cmdline.txt