BaseTools: Fix two drivers include the same file issue

BaseTools: Fix two drivers include the same file issue

Two drivers include the same PCD file, the PCD value in the first
driver is correct, but it in the second driver is incorrect.

DSC:
[Components]
  Testpkg/Testdriver1.inf {
  <PcdsFixedAtBuild>
  !include Test.txt
  }
  Testpkg/Testdriver2.inf {
  <PcdsFixedAtBuild>
  !include Test.txt
  }

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yunhua Feng <yunhuax.feng@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>