brew typecheck homebrew/services is looking a little better now?

- I did:

```shell
cd $(brew --repo homebrew/services)
mkdir sorbet/
cp $(brew --repo)/Library/Homebrew/sorbet/config sorbet/
brew typecheck homebrew/services
```

Library/Homebrew/dev-cmd/typecheck.rb

@@ -46,7 +46,7 @@ class Typecheck < AbstractCommand
       def run
         update = args.update? || args.update_all?
         tap_path = args.no_named? ? HOMEBREW_LIBRARY_PATH : args.named.to_paths(only: :tap).first
-        unless (tap_path/"sorbet").exist?
+        unless (tap_path/"sorbet").directory?
           raise UsageError, "Sorbet typechecking is not supported for the #{args.named.first} tap. " \
                             "Add a `sorbet/` directory with a config file to the tap to enable it."
         end
@@ -101,6 +101,7 @@ def run
           end
 
           srb_exec += ["--ignore", args.ignore] if args.ignore.present?
+          srb_exec += ["--dir", HOMEBREW_LIBRARY_PATH] unless tap_path == HOMEBREW_LIBRARY_PATH
           if args.file.present? || args.dir.present?
             cd("sorbet") do
               srb_exec += ["--file", "../#{args.file}"] if args.file