vulpix: pass -classpath to javac too

Otherwise the tastyBootstrap test failed when compiling the .java files
added in the previous commit that depend on scala-asm.

Author: smarter

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

@@ -324,7 +324,8 @@ trait ParallelTesting extends RunnerOrchestration { self =>
 
     protected def compile(files0: Array[JFile], flags0: TestFlags, suppressErrors: Boolean, targetDir: JFile): TestReporter = {
 
-      val flags = flags0 and ("-d", targetDir.getAbsolutePath)
+      val flags = flags0.and("-d", targetDir.getAbsolutePath)
+        .withClasspath(targetDir.getAbsolutePath)
 
       def flattenFiles(f: JFile): Array[JFile] =
         if (f.isDirectory) f.listFiles.flatMap(flattenFiles)
@@ -336,9 +337,7 @@ trait ParallelTesting extends RunnerOrchestration { self =>
         val fullArgs = Array(
           "javac",
           "-encoding", "UTF-8",
-          "-classpath",
-          s"${Properties.scalaLibrary}${JFile.pathSeparator}${targetDir.getAbsolutePath}"
-        ) ++ flags.all.takeRight(2) ++ fs
+        ) ++ flags.javacFlags ++ fs
 
         val process = Runtime.getRuntime.exec(fullArgs)
         val output = Source.fromInputStream(process.getErrorStream).mkString
@@ -366,7 +365,7 @@ trait ParallelTesting extends RunnerOrchestration { self =>
             }
         }
 
-      val allArgs = flags.withClasspath(targetDir.getAbsolutePath).all
+      val allArgs = flags.all
 
       // Compile with a try to catch any StackTrace generated by the compiler:
       try {

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

@@ -20,6 +20,14 @@ final case class TestFlags(
     TestFlags(defaultClassPath, s"$runClassPath${JFile.pathSeparator}$classPath", options)
 
   def all: Array[String] = Array("-classpath", defaultClassPath) ++ options
+
+  /** Subset of the flags that should be passed to javac. */
+  def javacFlags: Array[String] = {
+    val flags = all
+    val cp = flags.dropWhile(_ != "-classpath").take(2)
+    val output = flags.dropWhile(_ != "-d").take(2)
+    cp ++ output
+  }
 }
 
 object TestFlags {