On Linux, install the mold linker before building from source: the workspace
.cargo/config.toml links Linux builds with it, and Cargo applies that
configuration to a bare cargo build --release too, so a build without mold
fails at the link step. Release artefacts from make release or CI add neither
the frontend flag nor mold, though a flag the caller exports survives.
Weaver requires Rust 1.89 or newer to build from source because its
ortho-config dependency has the same minimum supported Rust version. The
repository's own checkout additionally needs the pinned Nightly toolchain
(nightly-2026-03-26): its .cargo/config.toml uses Nightly-only options, so
stable Rust is not sufficient for local Cargo builds there. The README lists
the toolchain setup.