Re-introduce erroneously removed line.

juliac/core/src/main/java/org/objectweb/fractal/juliac/Juliac.java

@@ -630,6 +630,7 @@ public class Juliac {
             List<SourceFile> sfs = new ArrayList<>();
             sfs.addAll(inputFiles);
             sfs.addAll(generatedFiles);
+            File classDir = getClassDir();
             compiler.compile(sfs,classDir);
         }