[bullhead][fp2] Package and implement libsparse

Package libsparse from the android project which provides the img2simg and simg2img commands. These split a large image for the system partition into seperate smaller chucks with sparse headers.

This is required for at least the Nexus 5x and the Fairphone 2 (#245) because it fixes the Invalid sparse file format at header magi error.

https://android.googlesource.com/platform/system/core/+/refs/heads/master/libsparse/