Proto default library path Custom protoc path may lead to the error /usr/bin/include: warning: directory does not exist.

[GollyTicker]

Custom protoc path may lead to the error /usr/bin/include: warning: directory does not exist. This can happen, when the user installed the libraries into a different path. We could deal with this in a better way. Furthermore, one needs to use a workaround when using a custom protoc and custom .protol-lib as both the users .proto files and the .proto-lib needs to be contained correctly.