libc.prx did not export wcstombs_s (sZLrjx-yEx4); only libSceAmpr did.
Ghost of Yotei imports it from libc.prx and stops at symbol resolution.
Move the implementation to libc next to wcsrtombs_s. libSceAmpr keeps
its export through an explicit-NID wrapper, because the NID patcher
leaves symbols that libc exports unrenamed in other libraries.