ohos-xts-acts: Add ltp to RRECOMMENDS

ACTS tests a subset of ltp open_posix_testsuite.
Spread will be used to selectively execute required tests.

Related-to: https://git.ostc-eu.org/OSTC/OHOS/components/staging/xts_acts/-/issues/15


Signed-off-by: Robert Drab <robert.drab@huawei.com>