bitbake: bitbake/lib/bb/build.py: fix the task flags cleandirs

The user manual said:

'cleandirs' - directories which should created before the task runs but should be empty

But it only removes the dir, doesn't create it

[YOCTO #5703]

(Bitbake rev: 0636797d75874ce4577f29011d69c56a4c6b9e89)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/build.py

@@ -154,6 +154,7 @@ def exec_func(func, d, dirs = None):
     if cleandirs:
         for cdir in d.expand(cleandirs).split():
             bb.utils.remove(cdir, True)
+            bb.utils.mkdirhier(cdir)
 
     if dirs is None:
         dirs = flags.get('dirs')