bitbake: runqueue: Fix unihash cache mismatch issues

Very occasionally we see errors in eSDK testing on the autobuilder where the task
hashes in the eSDK don't match what was just built. I was able to inspect one of
these build directories and noticed that the bb_unihashes.dat file in the eSDK
was zero sized. Whilst inspecting the code to understand the cause, I noticed that
updated hashes are not saved out in subsequent updates of the values in the rehash
process.

Add a missing sync call to ensure this happens.

(Bitbake rev: 81a6f490dd1f5f669c75cd2ceb1105ce7a09c6e4)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 7912dabbcf444a3c3d971cca4a944a8b931e301b)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -2381,6 +2381,9 @@ class RunQueueExecute:
                     self.rqdata.runtaskentries[hashtid].unihash = unihash
                     bb.parse.siggen.set_unihash(hashtid, unihash)
                     toprocess.add(hashtid)
+                if torehash:
+                    # Need to save after set_unihash above
+                    bb.parse.siggen.save_unitaskhashes()
 
         # Work out all tasks which depend upon these
         total = set()