We've seen occasional issues on the autobuilder where files appear during
do_populate_sysroot and this is due to the ptest installation happening
in parallel. This fixes the order to be deterministic.
(From OE-Core rev: 0ed1641d870f4bb5735aeeb7bd29cc196e61b7cc)
(From OE-Core rev: 96aa9bf8880088c9a710c86cc8ee106138152a98)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>