buildtest-TESTS and runtest-TESTS targets are required by ptest.
In order to have those targets in automake 1.13.4, serial-tests
should be specified since parallel test is assumed by default
and serial-tests is optional.
(From OE-Core rev: b7a0e1c351e396af6470e59c428128789295bd96)
Signed-off-by: Tudor Florea <tudor.florea@enea.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>