zshrc: fix error about dircolors not found on Mac. (git commit --amend)

zshrc

@@ -38,7 +38,9 @@ zstyle ':completion:*' completer _expand _complete _correct _approximate
 zstyle ':completion:*' format 'Completing %d'
 zstyle ':completion:*' group-name ''
 zstyle ':completion:*' menu select=2
-eval "$(dircolors -b)"
+if [ $UNAME != "Darwin" ]; then
+    eval "$(dircolors -b)"
+fi
 zstyle ':completion:*:default' list-colors ${(s.:.)LS_COLORS}
 zstyle ':completion:*' list-colors ''
 zstyle ':completion:*' list-prompt %SAt %p: Hit TAB for more, or the character to insert%s