BaseTools: Fixed Pcd value override issue.

1. Handle the Pcd maxsize issue for the case
that the length of Pcd value from CommandLine
bigger that its maxsize

2. The Pcd value override in commandline.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
(cherry picked from commit b854e2bf75)

BaseTools/Source/Python/Workspace/BuildClassObject.py

@@ -129,6 +129,8 @@ class StructurePcd(PcdClassObject):
         self.PkgPath = ""
         self.DefaultValueFromDec = ""
         self.ValueChain = dict()
+        self.PcdValueFromComm = ""
+        self.PcdFieldValueFromComm = collections.OrderedDict({})
     def __repr__(self):
         return self.TypeName
 
@@ -188,6 +190,8 @@ class StructurePcd(PcdClassObject):
             self.PcdDefineLineNo = PcdObject.PcdDefineLineNo if PcdObject.PcdDefineLineNo else self.PcdDefineLineNo
             self.PkgPath = PcdObject.PkgPath if PcdObject.PkgPath else self.PkgPath
             self.ValueChain = PcdObject.ValueChain if PcdObject.ValueChain else self.ValueChain
+            self.PcdValueFromComm = PcdObject.PcdValueFromComm if PcdObject.PcdValueFromComm else self.PcdValueFromComm
+            self.PcdFieldValueFromComm = PcdObject.PcdFieldValueFromComm if PcdObject.PcdFieldValueFromComm else self.PcdFieldValueFromComm
 
 ## LibraryClassObject
 #