Add external/timezone-boundary-builder to default

Add the external/timezone-boundary-builder project to the default
manifest. This git project contains information about time zone geo
boundaries.

clone-depth has been set to 2: the git project contains sizable binary
files, but it will be useful to compare consecutive versions.

Bug: 148653919
Test: None
Change-Id: I939c794b1c7536697729b2269e1e043a5d0664c7
1 file changed