sd-image: add preBuildCommands option (#501160)

      '';

    };

    preBuildCommands = mkOption {

      type = types.lines;

      example = literalExpression ''

        '''

          if [ ! -w "$root_fs" ]; then

            cp --no-preserve=mode "$root_fs" ./root-fs.img

            root_fs=./root-fs.img

          fi

          resize2fs $root_fs 15G

        '''

      '';

      default = "";

      description = ''

        Shell commands to run after the root filesystem image has been

        prepared, but before the final SD image is assembled.

        The path to the root filesystem image is available in the

        {var}`root_fs` shell variable. This hook can be used to modify

        the rootfs, for example to resize it or inject additional files.

        Note that when {option}`sdImage.compressImage` is disabled,

        {var}`root_fs` points to a read-only store path. To modify it,

        first copy it to a writable location and update {var}`root_fs`

        to point to the copy.

      '';

    };

    postBuildCommands = mkOption {

      type = types.lines;

      example = literalExpression "'' dd if=\${pkgs.myBootLoader}/SPL of=$img bs=1024 seek=1 conv=notrunc ''";

      default = "";

      description = ''

        Shell commands to run after the image is built.

        Can be used for boards requiring to dd u-boot SPL before actual partitions.

        Shell commands to run after the SD image has been assembled.

        The path to the image is available in the {var}`img` shell

        variable. This hook is typically used for boards that require

        writing a bootloader (such as u-boot SPL) to a fixed offset

        before the first partition.

      '';

    };

            zstd -d --no-progress "${config.sdImage.rootFilesystemImage}" -o $root_fs

          ''}

          ${config.sdImage.preBuildCommands}

          # Gap in front of the first partition, in MiB

          gap=${toString config.sdImage.firmwarePartitionOffset}