Fix abort regression.

Change https://googleplex-android-review.googlesource.com/#/c/249463/ set a
boolean prior to testing it meaning that all aborts were seen as recursive and
no meaningful log information was given.

Also a fix related to https://googleplex-android-review.googlesource.com/293665
where we were attempting to dump other threads stacks during aborting even
though those threads weren't suspended.

Change-Id: I1f848512c5e380529579db3d16bb8f5ddda36ad3
diff --git a/src/runtime_linux.cc b/src/runtime_linux.cc
index 0be6339..a4fc3af 100644
--- a/src/runtime_linux.cc
+++ b/src/runtime_linux.cc
@@ -236,7 +236,7 @@
   }
   handlingUnexpectedSignal = true;
 
-  gAborting = true;  // set before taking any locks
+  gAborting++;  // set before taking any locks
   MutexLock mu(Thread::Current(), *Locks::unexpected_signal_lock_);
 
   bool has_address = (signal_number == SIGILL || signal_number == SIGBUS ||