Fix loading untransformed executables again.

lib/src/executable.dart

Index: lib/src/executable.dart
diff --git a/lib/src/executable.dart b/lib/src/executable.dart
index 7e577d04256b5c2d9ef3d1856974182e557b5e16..863f306f672e01c03349298ddf37efffcd3faa6c 100644
--- a/lib/src/executable.dart
+++ b/lib/src/executable.dart
@@ -113,7 +113,7 @@ Future<int> runExecutable(Entrypoint entrypoint, String package,
   // If we're running an executable directly from the filesystem, make sure that
   // it knows where to load the packages. If it's a dependency's executable, for
   // example, it may not have the right packages directory itself.
-  if (executableUrl.scheme == 'file') {
+  if (executableUrl.scheme == 'file' || executableUrl.scheme == '') {
     // TODO(nweiz): use a .packages file once sdk#23369 is fixed.
     vmArgs.add('--package-root=${p.toUri(entrypoint.packagesDir)}');
   }