Create VCS backend for testers2

[chick]

• Create new VcsBackendAnnotation
• Create support utilities for Vcs building tools
  • CopyVpiFiles move vpi and header files into place
  • GenVcsVerilogHarness Compile stuff
  • VcsAnnotations control behavior of the Vcs backend
• Create VcsBackend, a trivial sub-classing of VerilatorBackend
• Create VcsExecutive
  • constructs VcsBackEnd requirements calls the constructor
• Create SimpleVcsTests
• Added String to Uniquify Verilator and Vcs Tests
• Suppress VCS tests if VCS not present in path
  • Updates to PR Add vcs backend support #58
  • Fixed CopyVpiFiles
    • looks like this might fail if early file was there but a late one wasn't
    • this code came from chisel-testers
  • Fix top level test names
    • behavior of "Testers2 with Vcs"
    • behavior of "Testers2 with Verilator"
  • Shortened VCS to just see if a simple circuit will build and simulate.
    • in long run we still need mechanism to run an arbitrary test with arbitrary backend
• Create new VcsBackendAnnotation
• Create support utilities for Vcs building tools
  • CopyVpiFiles move vpi and header files into place
  • GenVcsVerilogHarness Compile stuff
  • VcsAnnotations control behavior of the Vcs backend
• Create VcsBackend, a trivial sub-classing of VerilatorBackend
• Create VcsExecutive
  • constructs VcsBackEnd requirements calls the constructor
• Create SimpleVcsTests
• Added String to Uniquify Verilator and Vcs Tests
• Fixed CopyVpiFiles
  • looks like this might fail if early file was there but a late one wasn't
  • this code came from chisel-testers
• Fix top level test names
  • behavior of "Testers2 with Vcs"
  • behavior of "Testers2 with Verilator"
• Shortened VCS to just see if a simple circuit will build and simulate.
  • in long run we still need mechanism to run an arbitrary test with arbitrary backend

[chick]

Replacement for PR #58
That PR was very stale and had multiple merges of master this is a clean
rebase on current master

[ducky64]

Looks fine at a glance, probably doesn't need a super in-depth review for stuff going into legacy. I assume it's been tested somewhere?

Also, what happens if this is run on a platform without VCS (probably would be the case for many people)? Ideally it would give a skipped test warning, or just pass?

[chick]

The test of VCS gives a "Test Canceled: firrtl.FileUtils.isVCSAvailable was false" message