bitbake: hob/bitbake: save the description of a custom image

When an new image is saved, the dialog for this action has
a field for the description. Changed how an image is saved, by
appending the DESCRIPTION variable at the end of the .bb file.

[YOCTO #4193]
(Bitbake rev: 5629007f2b984005e3a8ac5d9b71422cbc2f1409)

Signed-off-by: Cristiana Voicu <cristiana.voicu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/cooker.py

@@ -1100,7 +1100,7 @@ class BBCooker:
 
         self.configuration.server_register_idlecallback(buildTargetsIdle, rq)
 
-    def generateNewImage(self, image, base_image, package_queue, timestamp):
+    def generateNewImage(self, image, base_image, package_queue, timestamp, description):
         '''
         Create a new image with a "require"/"inherit" base_image statement
         '''
@@ -1125,6 +1125,9 @@ class BBCooker:
             package_install += "\"\n"
             imagefile.write(package_install)
 
+            description_var = "DESCRIPTION = \"" + description + "\"\n"
+            imagefile.write(description_var)
+
         self.state = state.initial
         if timestamp:
             return timestr