Prepare scripts for major/minor API levels

For third_party/android_jar keep the current name scheme for
minor version 0, e.g.:

  third_party/android_jar/lib-v36

For other minor versions add the minor version, e.g.:

  third_party/android_jar/lib-v36.1

Change-Id: Ib06e0d7d551049ae10bc229a01c2cfbe62ff582e
diff --git a/tools/r8.py b/tools/r8.py
index a6bf42e..9b27fb5 100755
--- a/tools/r8.py
+++ b/tools/r8.py
@@ -56,7 +56,7 @@
     (options, args) = ParseOptions(sys.argv)
     r8_args = args[1:]
     if options.lib_android:
-        r8_args.extend(['--lib', utils.get_android_jar(options.lib_android)])
+        r8_args.extend(['--lib', utils.get_android_jar(options.lib_android, 0)])
     if options.lib_rt:
         r8_args.extend(['--lib', utils.RT_JAR])
     time_consumer = lambda duration: print_duration(duration, options)