BaseTools: the list and iterator translation

In python3,The keys of the dictionary not a list,It needs to be converted

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>

BaseTools/Source/Python/build/build.py

@@ -443,7 +443,7 @@ class BuildTask:
 
                 # get all pending tasks
                 BuildTask._PendingQueueLock.acquire()
-                BuildObjectList = BuildTask._PendingQueue.keys()
+                BuildObjectList = list(BuildTask._PendingQueue.keys())
                 #
                 # check if their dependency is resolved, and if true, move them
                 # into ready queue