Embed zucchini version info in target_files

external/zucchini/version_info.h contains version info for zucchini
diffing algorithm. OTA tools will use these version info to check for
compatibility and determine if zucchini can be used safely. Owners of
zucchini agreed to keep the format of version_info.h stable so it's
parser friendly.

Bug: 194237829
Test: m dist
Change-Id: If8e37533933b346d3f03adab9263679910ab328c