Absolutize typeshed path

Differential Revision: D88197568

Author: connernilsen

crates/pyrefly_config/src/config.rs

@@ -1096,6 +1096,9 @@ impl ConfigFile {
         if let Some(import_root) = &self.import_root {
             self.import_root = Some(import_root.absolutize_from(config_root));
         }
+        if let Some(typeshed_path) = &self.typeshed_path {
+            self.typeshed_path = Some(typeshed_path.absolutize_from(config_root));
+        }
         self.python_environment
             .site_package_path
             .iter_mut()