"ld -l<NULL>" == "ld -la" -- why?

[Guy Harris]

>I think liba.a didn't survive past Sixth Edition UNIX (circa 1976),

As I remember, you're right.

For those of you who are wondering "what the hell is 'liba.a'?", it was,
as I remember, a library of routines usable from assembler-language
programs (hence the "a" in "liba", just as with the "c" in "libc"). 
Back in the V6 days, there was still a fair bit of assembler code in
UNIX utilities (the original V6 "ar" was, as I remember, assembler code,
as was the original V6 "nroff", and I think some other stuff like the
"mkdir" command).