If sstate-inputdirs and sstate-outputdirs don't match with ending '/'
characters, the manifest file can end up corrupted. This change
ensures the metadata is consistent in ending do_populate_root tasks
with this character to avoid manifest file corruption.
(From OE-Core rev: 3910eaf88d14904eef85b9e391387547df7fc54e)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>