BaseTools: Extend the Macro used in the FDF !include statement

BaseTools: Extend the Macro used in the FDF !include statement

Current it only support the system environment variables in the !include
statement, $(WORKSPACE), $(PACKAGES_PATH), $(EFI_SOURCE), $(EDK_SOURCE),
$(ECP_SOURCE), this patch extend the usage to support the Global macros
and the macro which defined before the statement.

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>