BaseTools: Improve build performance of structure PCD value generation

Add cache for building PcdValueInit.c. If PcdValueInit.c is not changed,
it will not be regenerated.

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>

BaseTools/Source/Python/GenFds/GenFds.py

@@ -326,6 +326,7 @@ def main():
                                     FvObj.FvRegionInFD = RegionObj.Size
                                     RegionObj.BlockInfoOfRegion(FdObj.BlockSizeList, FvObj)
 
+        GlobalData.BuildOptionPcd     = Options.OptionPcd if Options.OptionPcd else {}
         """Call GenFds"""
         GenFds.GenFd('', FdfParserObj, BuildWorkSpace, ArchList)