missing errno assigns

chimera linux has a patch for some missing errno assigns: https://github.com/chimera-linux/cports/blob/187f77f7f29304f886648522d36f66a1a3514409/main/musl/patches/mimalloc-errno.patch

that was needed to fix cases of e.g. allocating some huge amount of memory (like 1tb when host has 16gb) where the allocation fails, and a null pointer is returned, but the corresponding errno is not set to enomem so the application doesn't handle it since it expects it to be set (per the malloc api). perhaps this fix should be applied here too?

Start by reviewing the Chimera Linux mimalloc-errno.patch linked in the issue and locating the corresponding allocation-failure paths in mimalloc. Verify which failures return NULL without setting ENOMEM, then add or update focused coverage so the relevant malloc API behavior is confirmed.

Written by the indexing model from the issue text.