refactor: add localBin, goBin & rustBin into PATH env

home/darwin/shell.nix

@@ -1,9 +1,9 @@
-let
-  envExtra = ''
+{lib}: let
+  envExtra = lib.mkAfter ''
     export PATH="$PATH:/opt/homebrew/bin:/usr/local/bin"
   '';
   # copied from the content generated by `conda init bash`
-  initExtra = ''
+  initExtra = lib.mkAfter ''
     arch=$(uname -m)
 
     if [ "aarch64" = "$arch" ] ||  [ "arm64" = "$arch" ]; then