The bug is for build output files it still use mws.join function, it
cause maybe we will get the build output files in the PACKAGES_PATH
because mws.join will try WORKSPACE first, if the file doesn't exist
then try PACKAGES_PATH. But for build output, we expected it should
relative to WORKSPACE.
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>