Fix Map type

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -159,7 +159,7 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
      */
     class Worker1(needsOutFolder: Boolean) {
 
-      val caseInsensitively = scala.collection.mutable.Map.empty[String, Symbol]
+      val caseInsensitively = scala.collection.mutable.HashMap.empty[String, Symbol]
 
       def run(): Unit = {
         while (true) {