bitbake/gcc: Enable a shared common source tree

This patch is a quick proof of concept to show how source code could
be shared between recipes which use ${B} to have a separate build
directory compared to source directory ${S}.

Issues:

a) gcc uses sed and creates config files against ${S} which means
the directory should not be shared. Need to change the way that works.

b) Could be extended to cover eglibc except there is a patch applied
against nativesdk versions which again makes the source incompatible.

c) Need to clean up the layout in work-shared and make a directory level deeper
to ensure patch separation.

d) clean task does not remove stamps

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -105,6 +105,11 @@ class RunQueueScheduler(object):
             if self.rq.runq_running[taskid] == 1:
                 continue
             if self.rq.runq_buildable[taskid] == 1:
+                fn = self.rqdata.taskData.fn_index[self.rqdata.runq_fnid[taskid]]
+                taskname = self.rqdata.runq_task[taskid]
+                stamp = bb.build.stampfile(taskname, self.rqdata.dataCache, fn)
+                if stamp in self.rq.build_stamps.values():
+                    continue
                 return taskid
 
     def next(self):
@@ -1010,6 +1015,7 @@ class RunQueueExecute:
         self.runq_complete = []
         self.build_pids = {}
         self.build_pipes = {}
+        self.build_stamps = {}
         self.failed_fnids = []
 
     def runqueue_process_waitpid(self):
@@ -1024,6 +1030,7 @@ class RunQueueExecute:
         del self.build_pids[result[0]]
         self.build_pipes[result[0]].close()
         del self.build_pipes[result[0]]
+        del self.build_stamps[result[0]]
         if result[1] != 0:
             self.task_fail(task, result[1]>>8)
         else:
@@ -1312,6 +1319,7 @@ class RunQueueExecuteTasks(RunQueueExecute):
 
             self.build_pids[pid] = task
             self.build_pipes[pid] = runQueuePipe(pipein, pipeout, self.cfgData)
+            self.build_stamps[pid] = bb.build.stampfile(taskname, self.rqdata.dataCache, fn)
             self.runq_running[task] = 1
             self.stats.taskActive()
             if self.stats.active < self.number_tasks: