Currently the code gives tracebacks if there are no recipes to be built in a
BuildStarted event. Parse the list into a string rather than just taking the
first item. There is nothing special about the first time.
(From OE-Core rev: 684a3d56ef393b56f38d3272f8865f6225a282ab)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>