snapshot.debian.org intermittently 503s during the musl sysroot build and
blocks releases (v1.14.0-lx.2-rc.1 failed twice on it). actions/cache also
misses across tag builds (ref-scoping). Add a producer workflow that uploads
the built toolchain to a musl-toolchain-cache release, and a restore step in
lx-release.yml that pulls it on cache-miss before falling back to
snapshot.debian.org. Both workflows are lx-owned; zero upstream diff.
Leadaxe
5e345ffe48