bitbake: toasterui: Show in the log that ToasterUi is ready to receive events.

Issue: TA53702

It was observed that a sequence in a script such as
   bitbake --server-only ..
   bitbake --observe-only ..
   bitbake <some target>
could generate events from the server to the observer before
the observer was ready to read the events, and the early events
of builds were consistently dropped.  Adding a "ready" note in the
log allows the script to scan for that message before proceeding
to building a target.

(Bitbake rev: 9949948f92bbe2717a05a380d3df63a332d39c9a)

Signed-off-by: Dave Lerner <dave.lerner@windriver.com>
Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/ui/toasterui.py

@@ -91,6 +91,7 @@ def main(server, eventHandler, params ):
     errors = 0
     warnings = 0
     taskfailures = []
+    first = True
 
     buildinfohelper = BuildInfoHelper(server, build_history_enabled)
 
@@ -98,6 +99,9 @@ def main(server, eventHandler, params ):
     while True:
         try:
             event = eventHandler.waitEvent(0.25)
+            if first:
+                first = False
+                logger.info("ToasterUI waiting for events")
 
             if event is None:
                 if main.shutdown > 0: