Broaden scope of gAborting. Fixes hang in HandleUnexpectedSignal.

Change-Id: I4c29cd7b67f07bb9f99c308feac5a3d6c236bc2b
diff --git a/src/logging.cc b/src/logging.cc
index 5680ed0..9dde963 100644
--- a/src/logging.cc
+++ b/src/logging.cc
@@ -25,6 +25,8 @@
 
 LogVerbosity gLogVerbosity;
 
+bool gAborting = false;
+
 static LogSeverity gMinimumLogSeverity = INFO;
 static std::string* gCmdLine;
 static std::string* gProgramInvocationName;