BaseTools: Fix incremental build failure that override file be removed

Fix a Incremental build failure. The case is: Both A and B package will
include a same .h file, and in the driver's packages section, A
package is listed before B package, so we will use the .h file in the A
package and build success, then we directly delete the .h file in package
A, it cause increment build failure since in the AutoGenTimeStamp file
the .h file in A can't be found.

Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/Python/AutoGen/AutoGen.py

@@ -4210,6 +4210,8 @@ class ModuleAutoGen(AutoGen):
         with open(self.GetTimeStampPath(),'r') as f:
             for source in f:
                 source = source.rstrip('\n')
+                if not os.path.exists(source):
+                    return False
                 if source not in ModuleAutoGen.TimeDict :
                     ModuleAutoGen.TimeDict[source] = os.stat(source)[8]
                 if ModuleAutoGen.TimeDict[source] > DstTimeStamp: