A couple of logging changes people have asked for.

How many threads dex2oat uses, and more detail about heap trimming.

Change-Id: Id60dbedf2480c639dc8c38b4a59eb0b15eb3b912
diff --git a/src/dex2oat.cc b/src/dex2oat.cc
index 7a6829e..c4ca894 100644
--- a/src/dex2oat.cc
+++ b/src/dex2oat.cc
@@ -110,7 +110,8 @@
 
   ~Dex2Oat() {
     delete runtime_;
-    LOG(INFO) << "dex2oat took " << PrettyDuration(NanoTime() - start_ns_);
+    const size_t thread_count = static_cast<size_t>(sysconf(_SC_NPROCESSORS_ONLN));
+    LOG(INFO) << "dex2oat took " << PrettyDuration(NanoTime() - start_ns_) << " (threads: " << thread_count << ")";
   }
 
   // Make a list of descriptors for classes to include in the image