On Windows, `npm_config_prefix` is resolved with `cd` + `pwd` so it can be compared with `$NVM_DIR`.
When the directory does not exist yet, that resolution fails,
the value becomes empty, and the check is skipped.
Keep the value as given in that case, like on other systems.
Assisted-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Wei-Lun Li <b84330808@gmail.com>