Add internal.bzl to EXTRA_DIST. (#8663)
Add internal.bzl to EXTRA_DIST. (#8663)

internal.bzl is required to load java/core/BUILD and java/lite/BUILD, so it must be distributed.
google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf