Misc compiler warning fixes in lib/libc

[asomers]

Summary

Misc compiler warning fixes in lib/libc

[imp]

lib/libc/gen/auxv.c

276

Shouldn't we declare buflen to be a size_t instead?

[asomers]

lib/libc/gen/auxv.c

276

Can't, because _elf_aux_info must have the same signature as elf_aux_info

[imp]

lib/libc/gen/auxv.c

276

Then maybe we should widen buflen to size_t instead of narrowing the return value of strlcpy.

[imp]

btw, the rest of the changes look totally fine. Sorry to be so nitpicky over this one...

lib/libc/gen/auxv.c

276

and do we need to make sure buflen isn't less than zero?

[asomers]

Handle buflen more carefully in _elf_aux_info

[kevans]

lib/libc/gen/auxv.c

276

I would've perhaps opted to just widen it for this one comparison after checking that it's not negative above, but I think it's fine either way.