This adds a mechanism for the unittests to be run with the TreadleBackend

This mechanism is not enabled and should not change the behavior of existing tests
A following PR will deliver a switch that will allow changing the backend.
The reasons for this PR
- Treadle tests run much faster, enabling quicker debugging and CI cycles
- This will help ensure fidelity of Treadle to the Verilator backend

A few tests are marked as verilator only due to black box limitations

Change treadle to a direct dependency

I tried to make it a test only dependency but the TesterDriver sits in src/main requiring that
regular compile have access to treadle

Oops, made treadle the default

A number of changes in response to @ducky64 review
- made backend check clearer and add error handling for multiple backends specified
- Fixed duplicate TargetDirAnnotation uses in Treadle backend
- Cleaned up BlackBox test formatting
- Undid unnecessary debugging changes from Counter
- Undid .gitignore change, that should be on another PR

A number of changes in response to @ducky64 review
- Undid debugging changes made to BitWiseOps

1 files changed, 2 insertions, 1 deletions

diff --git a/build.sbt b/build.sbt
index 47925b6f..ab280be8 100644
--- a/build.sbt
+++ b/build.sbt
@@ -29,7 +29,8 @@ def javacOptionsVersion(scalaVersion: String): Seq[String] = {
 }
 
 val defaultVersions = Seq(
-  "edu.berkeley.cs" %% "firrtl" % "1.4-SNAPSHOT"
+  "edu.berkeley.cs" %% "firrtl" % "1.4-SNAPSHOT",
+  "edu.berkeley.cs" %% "treadle" % "1.3-SNAPSHOT"
 )
 
 lazy val commonSettings = Seq (