From Konrad Eisele:

> like with cmd_ld in scripts/Makefile.lib having possibility to add 
> customflags with cmd_objcopy would be nice. When building a
> ROMKernel I'd like to use:
> OBJCOPYFLAGS_rompiggydata := --remove-section=.text
> OBJCOPYFLAGS_$(MODEL)piggytext := --only-section=.text