For run_on_as_app, use r8 jar to find version and not Version.java

Change-Id: I38dd0b4b72cce0f4a7956f1b4d4868ab0a88bcf5
diff --git a/tools/archive.py b/tools/archive.py
index ecc0c04..c842c69 100755
--- a/tools/archive.py
+++ b/tools/archive.py
@@ -26,6 +26,7 @@
   return result.parse_args()
 
 def GetToolVersion(jar_path):
+  # TODO(mkroghj) This would not work for r8-lib, maybe use utils.getR8Version.
   output = subprocess.check_output([
     jdk.GetJavaExecutable(), '-jar', jar_path, '--version'
   ])