[next-rebased] Fix "Could not locate script 'default-nodes/rescan.lua'" error

When I tried to run the next-rebased branch of wireplumber, I got the error in the title. This is because lookup_dirs with WP_LOOKUP_DIR_ENV_DATA or WP_LOOKUP_DIR_ENV_TEST_SRCDIR was broken in commit aa2f7e9f.

This is a patch to fix this problem: 0001-lib-wp-Fix-lookup_dirs-with-WP_LOOKUP_DIR_ENV_DATA-o.patch

I can't create a merge request for it because I can't fork the wireplumber repo with a new account.