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, 2 deletions

diff --git a/src/test/scala/chiselTests/ExtModule.scala b/src/test/scala/chiselTests/ExtModule.scala
index 582a05ae..39cd65dc 100644
--- a/src/test/scala/chiselTests/ExtModule.scala
+++ b/src/test/scala/chiselTests/ExtModule.scala
@@ -62,11 +62,11 @@ class MultiExtModuleTester extends BasicTester {
 class ExtModuleSpec extends ChiselFlatSpec {
   "A ExtModule inverter" should "work" in {
     assertTesterPasses({ new ExtModuleTester },
-        Seq("/chisel3/BlackBoxTest.v"))
+        Seq("/chisel3/BlackBoxTest.v"), TesterDriver.verilatorOnly)
   }
   "Multiple ExtModules" should "work" in {
     assertTesterPasses({ new MultiExtModuleTester },
-        Seq("/chisel3/BlackBoxTest.v"))
+        Seq("/chisel3/BlackBoxTest.v"), TesterDriver.verilatorOnly)
   }
   "DataMirror.modulePorts" should "work with ExtModule" in {
     ChiselStage.elaborate(new Module {