how can I customize linkdirs when creating packages for xmake repo?

[qiuwei]

I would like to do something like:

add_linkdirs("lib/" .. package:config("project_name"))

Where project_name is of type string and should be provided by the package user.
However, it seems invalid.
How could I achieve this?

[waruqi]

package("xxx")
     on_load(function (package)
          package:add("linkdirs", path.join("lib", package:config("project_name")))
     end)

[qiuwei]

Many thanks! saved my day!