Running "-c cleanall" on shared DL_DIR and SSTATE_DIR is antisocial.
It leads to hard to debug races where we wonder why files disappear
and reappear from those directories.
Fix this by using a specific set of directories for these tests. This
avoids a long standing bug on the autobuilder where aspell and man
sources would disappear.
[YOCTO #6276]
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
