bitbake: Hob: log for Hob and allow users to show logs after successful build

If users build images in Hob, record logs and allow users to retrieve the lo
after successful build.

The logs are generated if and only if:
      - users do "just bake"
      - users do "build image" after "build packages"
      - users do "build packages" only

[YOCTO #1991]

(Bitbake rev: 291289787bb042b99f0599babc2d67c220aadb87)

Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: Liming An <limingx.l.an@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/ui/crumbs/hobeventhandler.py

@@ -390,6 +390,9 @@ class HobHandler(gobject.GObject):
     def reset_build(self):
         self.build.reset()
 
+    def get_logfile(self):
+        return self.server.runCommand(["getVariable", "BB_CONSOLELOG"])
+
     def _remove_redundant(self, string):
         ret = []
         for i in string.split():