Support building of YouTube 16.10

This extends run_on_app.py to build the required desugared library DEX
using tracereferences followed by R8.

Bug: 183704605
Change-Id: I361ce39db94a1fb267c854320d0ab497b8048ea6
diff --git a/tools/toolhelper.py b/tools/toolhelper.py
index 1cfd0f0..b66b70f 100644
--- a/tools/toolhelper.py
+++ b/tools/toolhelper.py
@@ -41,6 +41,8 @@
     cmd.extend(['-cp', utils.R8LIB_JAR, 'com.android.tools.r8.D8'])
   elif tool == 'r8lib-r8':
     cmd.extend(['-cp', utils.R8LIB_JAR, 'com.android.tools.r8.R8'])
+  elif tool == 'r8lib-tracereferences':
+    cmd.extend(['-cp', utils.R8LIB_JAR, 'com.android.tools.r8.tracereferences.TraceReferences'])
   else:
     cmd.extend(['-jar', utils.R8_JAR, tool])
   lib, args = extract_lib_from_args(args)