//! Re-emits the CoinHSL `-rpath` against this package's test binaries.
//!
//! `cargo:rustc-link-arg` applies only to targets in the package that
//! emitted it, so `crates/pounce-hsl/build.rs`'s copy reaches nothing
//! downstream and an MA57-linked target dies at process start with
//! "Library not loaded: @rpath/libcoinhsl.dylib" (gh#811). The directory
//! travels as build-script metadata instead: pounce-hsl declares
//! `links = "coinhsl"` and emits `cargo:rpath=<dir>`, which cargo hands
//! to each **direct** dependent's build script as `DEP_COINHSL_RPATH` —
//! hence the optional `pounce-hsl` dependency in `Cargo.toml`, which is
//! there to make this crate a direct dependent and for nothing else.
//!
//! Kept in sync with the identical copies in `pounce-algorithm`,
//! `pounce-cli`, `pounce-cinterface` and `pounce-py`.