Enable testing without rocket-chip

[seldridge]

It would be beneficial to enable testing that did not rely on instantiating a rocket chip. This is faster, enables VCD debugging, and would enable unit testing of individual modules. The problem relates to properly pulling in all the dependencies and parameters needed by X-FILES/DANA.

It seems like there are four ways of pulling in dependencies:

• Defining dependencies as projects, e.g., lazy val rocket = project in file(...). This has problems related to the project living in a separate directory.
• Defining dependencies as a RootProject, e.g., lazy val rocketChip = RootProject(file(...)). This is questionable because an entire rocket-chip isn't needed.
• Defining dependencies as unmanaged source, e.g., unmanagedSourceDirectories in Compile += baseDirectory.value / "../rocket/src/main/scala". This works alright for everything except Chisel.
• Defining dependencies as libraries, e.g., pulling Chisel locally or from the Maven repo.

A mixture of these seems to work except I'm unable to pull in all the requisite parameters. If I don't include the rocket-chip configuration, then I have trouble with PAddrBits. However, if I do include the rocket-chip configuration, I have trouble with TLId.

There should be a way to do this and do it cleanly, but I'm at a loss presently.