BaseTools:Incremental build not work if VPD values in DSC changed by -D

BaseTools:Incremental build not work if VPD values in DSC changed by -D

If a -D flag is passed into build that selects different lines in
[PcdsDynamicExVpd], then build does not see any changes to the timestamp
of the DSC file and the VPD tool is not used to regenerate the VPD
region based in the statements that are active. so we changed the detect
condition and use SaveFileOnChange function to generate VPD.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19767 6f19259b-4bc3-4df7-8a09-765794883524