Integrate Bazel build targets into Xcode project

[jerrymarino]

XCHammer was originally designed to produce a great user experience for local on Xcode development. However, building with Bazel is still useful and widely preferred.

The current approach to achieving this is not very maintainable, documented, or ideal:

• Create an Xcode workspace
• Put XCHammer projects in that workspace
• Create a separate Xcode project and targets that run bazel ( i.e. a Tulsi gen'd project with no files )

Come up with a way to integrate this into XCHammer.

[jerrymarino]

#24 addresses the first part of getting this to work. The remaining effort includes adding the toolchain to support debugger integration