liblink/obj6.c uses ctxt->debugstack to emit stack underflow checks. The flag was
meant to be initialized from -K 6l flag.
But now liblink is invoked from the compiler. And the compiler does not initialize
ctxt->debugstack. Moreover the compiler already uses -K flag for a different purpose.
I suspect this relates to a bunch of other flags as well.
We need to choose some other names for the old linker flags and read them in all users
of liblink.