docs: improve prerequisites for OSX users

.wordlist.txt

@@ -77,6 +77,7 @@ config
 configs
 const
 constantish
+coreutils
 cors
 cryptographic
 dApp

CONTRIBUTING.md

@@ -7,6 +7,13 @@ Thanks for your interest in contributing to Lodestar. It's people like you that
 - :gear: [NodeJS](https://nodejs.org/) (LTS)
 - :toolbox: [Yarn](https://yarnpkg.com/)
 
+### MacOS Specifics
+
+When using MacOS, there are a couple of extra prerequisites that are required.
+
+- python
+- coreutils (e.g. via `brew install coreutils`)
+
 ## Getting Started
 
 - :gear: Run `yarn` to install dependencies.

packages/db/test/unit/controller/level.test.ts

@@ -144,7 +144,8 @@ describe("LevelDB controller", () => {
           return "gdu";
         }
       } catch {
-        /* no-op */
+        /* eslint-disable no-console */
+        console.error("Cannot find gdu command, falling back to du");
       }
     }
     return "du";