bitbake-dev: Include the worker's PID in events

When the runqueue forks off we save the pid inside the event module for that
thread. When we next fire an event then that PID gets included in the events.

bitbake-dev/lib/bb/event.py

@@ -25,12 +25,17 @@ BitBake build tools.
 import os, re
 import bb.utils
 
+# This is the pid for which we should generate the event. This is set when
+# the runqueue forks off.
+worker_pid = 0
+
 class Event:
     """Base class for events"""
     type = "Event"
 
     def __init__(self, d):
         self._data = d
+        self.pid = worker_pid
 
     def getData(self):
         return self._data