Filter out the dot directories form tests

Author: Kordyjan

compiler/test/dotty/tools/vulpix/FileFilter.scala

@@ -23,4 +23,8 @@ object FileFilter {
   object NoFilter extends FileFilter {
     def accept(file: String) = true
   }
+
+  object ExcludeDotFiles extends FileFilter {
+    def accept(file: String) = !file.startsWith(".")
+  }
 }

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -1411,7 +1411,7 @@ trait ParallelTesting extends RunnerOrchestration { self =>
   private def compilationTargets(sourceDir: JFile, fileFilter: FileFilter = FileFilter.NoFilter): (List[JFile], List[JFile]) =
     sourceDir.listFiles.foldLeft((List.empty[JFile], List.empty[JFile])) { case ((dirs, files), f) =>
       if (!fileFilter.accept(f.getName)) (dirs, files)
-      else if (f.isDirectory) (f :: dirs, files)
+      else if (f.isDirectory && FileFilter.ExcludeDotFiles.accept(f.getName)) (f :: dirs, files)
       else if (isSourceFile(f)) (dirs, f :: files)
       else (dirs, files)
     }