🩹 Fix failing bundle step

The Bundle CI step is failing due to an `artifacts` directory sometimes
already existing. This adds the `-p` flag to `mkdir` to ensure that,
if the directory already exists, the script won't fail.

.github/actions/cargo-bundle/action.yaml

@@ -44,7 +44,7 @@ runs:
         install_name_tool -add_rpath "@executable_path/../Frameworks" ${app_dir}/Contents/MacOS/*
 
         bundle_dir=$(cd ${app_dir}/..; pwd)
-        mkdir "${target_dir}/artifacts"
+        mkdir -p "${target_dir}/artifacts"
         tar                                                                    \
           --create                                                             \
           --verbose                                                            \