shoving a nar dump directly into a framed sink created a bunch of tiny
frames, each of which requires at least two syscalls to read. this can
lead to immense performance loss when using a daemon; we have seen 15%
in benchmarks on main and even more with async code involved ... oops.
Change-Id: I8529506e3de74d92834d1f4ee228dcaf32eb756c
eldritch horrors
d5cfc6f19c