Adding eStopReasonThreadExiting and fixing the handling of this state on Linux.

llvm-svn: 170800
diff --git a/lldb/tools/driver/Driver.cpp b/lldb/tools/driver/Driver.cpp
index 96fd4cf..623eddf 100644
--- a/lldb/tools/driver/Driver.cpp
+++ b/lldb/tools/driver/Driver.cpp
@@ -807,6 +807,7 @@
                 case eStopReasonSignal:
                 case eStopReasonException:
                 case eStopReasonExec:
+                case eStopReasonThreadExiting:
                     if (!other_thread.IsValid())
                         other_thread = thread;
                     break;