README.md: put Cachix cache setup before Building the project

Author: Anton-Latukha

README.md

@@ -70,6 +70,15 @@ hnix --eval -E '(import <nixpkgs> {}).pkgs.hello' --repl
 Use the `:help` command for a list of all available REPL commands.
 
 
+## Cachix prebuild binary caches
+
+To autoload prebuild project dependencies - please, enable the official HNix Cachix binary cache:
+
+1. Go through https://cachix.org/ and set it up.
+
+2. Run: `cachix use hnix`
+
+
 ## Building
 
 ### With full debug info
@@ -108,15 +117,6 @@ cabal v2-build
 cabal v2-run hnix -- <args> +RTS -p
 ```
 
-## Cachix prebuild binary caches
-
-To autoload prebuild project dependencies - please, enable the official HNix Cachix binary cache:
-
-1. Go through https://cachix.org/ and set it up.
-
-2. Run: `cachix use hnix`
-
-
 ## Contributing
 
 1. If something in the [quests](https://github.com/haskell-nix/hnix/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22+no%3Aassignee) looks interesting, look through the thread and leave a comment taking it, to let others know you're working on it.