My recollection is that COPTS used to be a make variable, that is only set by users, but never set by system (in-tree) makefiles. Now there are not many but some places where COPTS are set by system makefiles. i believe that COPTS+=-fxxx and COPTS+=-DXXX are replaced with CFLAGS+=-fxxx and CPPFLAGS+=-DXXX respectively.