* scripts/guix.in: Remove empty surrounding ‘let’. Define 'main' as the
procedure called when running the script.
(maybe-augment-load-paths!): Rename to ...
(augment-load-paths!): ... this. Use 'and=>' for 'file-exists?'.
(run-guix-main): Rename to ...
(main): ... this. Call 'augment-load-paths!'.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>