sstate: Set umask to 002 before packaging runs

Otherwise we might end up creating directories under sstate-cache with whatever
random umask has been selected for the task that we're trying to package.  This
would be a bad thing since it might result in losing group write access for
newly created dirs, and/or losing group read access for the sstate files
themselves.

(From OE-Core rev: d8c4f442c41bf3ac5e064630657cd3fa1b5c43b1)

Signed-off-by: Phil Blundell <philb@gnu.org>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/sstate.bbclass

@@ -532,7 +532,11 @@ python sstate_task_postfunc () {
     sstate_install(shared_state, d)
     for intercept in shared_state['interceptfuncs']:
         bb.build.exec_func(intercept, d)
+    omask = os.umask(002)
+    if omask != 002:
+       bb.note("Using umask 002 (not %0o) for sstate packaging" % omask)
     sstate_package(shared_state, d)
+    os.umask(omask)
 }