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

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 https://github.com/grpc/grpc/issues/6784

This is for the same reasons as ParseJson, that is so that we can limit
the scope of the proto namespace differences between internal and
external.

This reverts commit d88e15ce.

files