how to install from binary

[Mason Hock <masonhock@gmail.com>]

Guix seems to be building everything from source, which can take a
while. As per these instructions I tried

# cd [prefix]/share/guix/hydra.gnu.org.pub
# guix archive --authorize < hydra.gnu.org.pub
and got

guile: warning: failed to install locale
warning: failed to install locale: Invalid argument

with no other output. I get that error almost every time I try to do
something with Guix and it usually works anyway. Since I got no other
errors I just kept going with

$ guix build emacs --dry-run

and got "The following derivations would be built:" so apparently it
did not work.

During an installation I do see a lot of "updating list of substitutes"
messages, but I also frequently see the word "build" and a lot of .c
and .h files go by, which combined with the long installation time
makes me doubt that it is actually downloading binaries from the
substitutes and installing them.