bitbake: add option to write offline event log file

This patch adds a "-w/--write-log" option to bitbake
that writes an event log file for the current build.

The name of the file is passed as a parameter to the "-w"
argument. If the parameter is the empty string '', the file
name is generated in the form bitbake_eventlog_DATE.json,
where DATE is the current date and time, with second precision.

The "-w" option can also be supplied as the BBEVENTLOG
environment variable.

We add a script, toater-eventreplay, that reads an event
log file and loads the data into a Toaster database, creating
a build entry.

We modify the toasterui to fix minor issues with reading
events from an event log file.

Performance impact is undetectable under no-task executed builds.

(Bitbake rev: 1befb4a783bb7b7b387d4b5ee08830d9516f1ac2)

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

bitbake/lib/bb/cookerdata.py

@@ -139,6 +139,7 @@ class CookerConfiguration(object):
         self.dry_run = False
         self.tracking = False
         self.interface = []
+        self.writeeventlog = False
 
         self.env = {}