The override is [here](https://github.com/purpleprotocol/mimalloc_rust/blob/59d7ee3ba7aa030b46a7cf721720f63a579b7fdb/libmimalloc-sys/build.rs#L28-L34). The polars project builds an unloadable binary because of this override in mimalloc, see this bug report: https://github.com/rust-lang/rust/issues/140092#issuecomment-2817368209
The override is here.
The polars project builds an unloadable binary because of this override in mimalloc, see this bug report: rust-lang/rust#140092 (comment)