Fix Benchmarks.scala

Author: odersky

bench/src/main/scala/Benchmarks.scala

@@ -1,7 +1,7 @@
 package dotty.tools.benchmarks
 
 import dotty.tools.dotc._
-import core.Contexts.Context
+import core.Contexts.{Context, CState}
 import dotty.tools.FatalError
 import reporting._
 
@@ -94,6 +94,7 @@ class CompilerOptions {
 class Worker extends Driver {
   // override to avoid printing summary information
   override  def doCompile(compiler: Compiler, fileNames: List[String])(implicit ctx: Context): Reporter =
+    given CState = ctx.cstate
     if (fileNames.nonEmpty)
       try {
         val run = compiler.newRun