Set detail message on exceptions for unstarted runtimes.

Change-Id: I7fcc9cc81ac33b1cdb322069c517bfdb31db2ac7
diff --git a/src/thread.cc b/src/thread.cc
index 014e2f0..8b10ccd 100644
--- a/src/thread.cc
+++ b/src/thread.cc
@@ -1297,6 +1297,7 @@
     if (exception.get() != NULL) {
       ScopedJniThreadState ts(env);
       Throwable* t = reinterpret_cast<Throwable*>(ts.Self()->DecodeJObject(exception.get()));
+      t->SetDetailMessage(String::AllocFromModifiedUtf8(msg));
       ts.Self()->SetException(t);
     } else {
       LOG(ERROR) << "Couldn't throw new " << descriptor << " because JNI AllocObject failed: "