package.bbclass: Clear package directory copy before installing new files to prevent stale data

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

meta/classes/package.bbclass

@@ -283,6 +283,7 @@ python perform_packagecopy () {
 
 	# Start by package population by taking a copy of the installed 
 	# files to operate on
+	os.system('rm -rf %s/*' % (dvar))
 	os.system('cp -pPR %s/* %s/' % (dest, dvar))
 }