Use override when adding to LDFLAGS and NASMFLAGS in makefile
Use override when adding to LDFLAGS and NASMFLAGS in makefile

This should ensure that the makefile works properly in the case that a
user sets LDFLAGS or NASMFLAGS manually when invoking `make`.  Without
it the additions to these variables won't happen.

UplinkCoder/SDC,UplinkCoder/SDC,deadalnix/SDC,UplinkCoder/SDC,SDC-Developers/SDC,SDC-Developers/SDC,SDC-Developers/SDC,deadalnix/SDC,deadalnix/SDC