Add protobuf and abseil-cpp projects

Protobuf is a dependency for building stg from sources, and abseil-cpp
is a dependency for protobuf.

Bug: 519089497
Change-Id: If3270ce9433f0f407dd662051edbc1b0d09fe840
(cherry picked from commit e305e7a2b94556e10ca5114b678dae2a1fc8d244)