core: Add script to check for possible shared library duplication

Running dupcheck.sh after a build on an image performs two checks:

  * Check for duplicate shared libraries by MD5.
  * Check for possible duplicate shared libraries by comparing .note
    and .text ELF sections.

This helps looking for unnecessary file duplication in the final images.

Test: after running the script, reports will be generated in the 'out'
directory.

Change-Id: I91c044a52002557fdc8dc65bfc9fd5f313ca00f3