In some cases, it's unfit to use "+=" in a conditional appending, we would
end up with the variable being set rather than being appended, which is not
it mean to.
(From OE-Core rev: 7eae843aaa4eaa534a2b825949563ca11bd3680c)
Signed-off-by: Ming Liu <ming.liu@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>