create_disk: Use bootupd for BIOS too

This uses the new https://github.com/coreos/bootupd/ 0.2.11 release.

src/create_disk.sh

@@ -396,11 +396,15 @@ cat > $rootfs/.coreos-aleph-version.json << EOF
 }
 EOF
 
-install_uefi() {
+install_via_bootupd() {
     # https://github.com/coreos/fedora-coreos-tracker/issues/510
     # See also https://github.com/ostreedev/ostree/pull/1873#issuecomment-524439883
     # Unshare mount ns to work around https://github.com/coreos/bootupd/issues/367
-    unshare -m /usr/bin/bootupctl backend install --src-root="${deploy_root}" "${rootfs}"
+    bootupd_args=()
+    if [ "${x86_bios_bootloader}" = 1 ]; then
+        bootupd_args+=("--device=$disk")
+    fi
+    chroot_run /usr/bin/bootupctl backend install --src-root="${deploy_root}" "${bootupd_args[@]}" "${rootfs}"
     # We have a "static" grub config file that basically configures grub to look
     # in the RAID called "md-boot", if it exists, or the partition labeled "boot".
     local target_efi="$rootfs/boot/efi"
@@ -475,29 +479,8 @@ generate_gpgkeys() {
 # Other arch-specific bootloader changes
 # shellcheck disable=SC2031
 case "$arch" in
-x86_64)
-    # UEFI
-    install_uefi
-    if [ "${x86_bios_bootloader}" = 1 ]; then
-        # And BIOS grub in addition.  See also
-        # https://github.com/coreos/fedora-coreos-tracker/issues/32
-        # Install BIOS/PReP bootloader using the target system's grub2-install,
-        # see https://github.com/coreos/coreos-assembler/issues/3156
-        chroot_run /sbin/grub2-install \
-            --target i386-pc \
-            --boot-directory $rootfs/boot \
-            --modules mdraid1x \
-            "$disk"
-    fi
-    ;;
-aarch64)
-    # Our aarch64 is UEFI only.
-    install_uefi
-    ;;
-ppc64le)
-    # to populate PReP Boot, i.e. support pseries
-    chroot_run /sbin/grub2-install --target=powerpc-ieee1275 --boot-directory $rootfs/boot --no-nvram "${disk}${PREPPN}"
-    install_grub_cfg
+x86_64|aarch64|ppc64le)
+    install_via_bootupd
     ;;
 s390x)
     ostree config --repo $rootfs/ostree/repo set sysroot.bootloader zipl