Demonstrate building an Objective-C library

[lacasseio]

A user can build an Objective-C library (shared and static) for the major operating system. Let's focus on building an approximation of what the objective-c-library plugin could look like. Avoid all configuration for now and focus on the source being in a single location (e.g. src/main/objective-c) and configuring the compiler flag by configuring the task directly (e.g. tasks.withType(ObjectiveCCompile)).