use homebrew to find homebrew-installed bins

Author: Dave Young

contributors/devel/development.md

@@ -162,7 +162,7 @@ You will want to include this block or something similar at the end of
 your `.bashrc` or shell init script:
 
 ```sh
-GNUBINS="$(find /opt/homebrew/opt -type d -follow -name gnubin -print)"
+GNUBINS="$(find `brew --prefix`/opt -type d -follow -name gnubin -print)"
 
 for bindir in ${GNUBINS[@]}
 do