`build_dep` was removed from crates.io for malicious code

`build_dep` attempted to send telemetry from the build environment to an
arbitrary URL.

The malicious crate had 1 version published on 2025-03-03, approximately 20
months before removal, and had no evidence of actual usage. This crate had no
dependencies on crates.io.

Thanks to [Bitbison](https://bitbison.io/) for the report.