Add super_empty.img to target-files and the update package.

super_empty.img is needed for "fastboot update" to work, as such, it
must be included in the update package. This change adds lpmake
parameters to misc_info.txt for add_img_to_target_files.py, and ensures
that lpmake is packaged with otatools.zip.

The build-superimage-target macro is now split into two functions - one
to generate the device-specific arguments, and another to build the full
command-line for convenience. The former is used to pass arguments
directly to add_img_to_target_files.

Bug: 113524256
Test: make updatepackage builds and includes super_empty.img
      make otatools includes lpmake

Change-Id: I25091c964b036beeea2a8b8f738e2c18937c1eb4