Previously grpc++_base was dependning on grpc what caused a transitive
dependency on ssl for grpc++_unsecure. Removing the grpc dependency
shouldn't cause any issue as grpc++_base is a filegroup and all library
using it already depends on grpc directly.

This fixes grpc#6784

This cmake file only builds the C and C++ code and all the third party
dependencies with very few configuration options but it supports
building on Linux and OSX as well as cross compiling.
(tested {Linux, OSX} -> Android { arm, aarch64, x86 })

This is the copy of the build.yaml changes from the following CL:
https://github.com/grpc/grpc/pull/4124/files#diff-5b123ecec7bf9d216a1323f790a0602a

* Add project name and version number
* Fix zlib dependency of grpc
* Include more target (all, protoc, tool groups)