CMake: Define `ABSL_ROOT_DIR` after populate call, shallow checkouts
CMake: Define `ABSL_ROOT_DIR` after populate call, shallow checkouts

The first part is to enable the UTF8 Range library shipped by protobuf to
build correctly. Otherwise, one had to run CMake twice (!) to configure.

To save time and bandwith, do not checkout the full Git history of
dependencies and do not checkout all of the submodules.

PiperOrigin-RevId: 490248302
Change-Id: Id98f5ca3d32af30562088af616da32899de51774

google/binexport,google/binexport,google/binexport