BaseTools tools_def.template: Add GCC link script option in ASLDLINK_FLAGS

BaseTools tools_def.template: Add GCC link script option in ASLDLINK_FLAGS

GCC link script is used to discard the unused section data from ELF image.
ASLDLINK_FLAGS requires it to remove the unnecessary section data, then
GenFw can be used to retrieve the correct data section from ELF image.

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