Rust builds from source on illumos — 1.98 and 1.99 in the cache

Rust is now a from-source build on illumos: rustc 1.98.0 and 1.99.0 are published to cache.solnix.io as real derivations (not a relabelled upstream tarball), each bootstrapped from the previous version. Every runtime reference of each output resolves to a path the cache already serves — libc, illumos-userland, gcc-14 runtime, openssl and zlib — with no wrapper and no LD_LIBRARY_PATH, so the closure is self-contained and reproducible. Both were verified end to end from an empty cache on real hardware: the signature check (cache.solnix.io-1 / 8UNr) passes for every path, a deliberately wrong key is rejected, and a recursive verify of each closure succeeds. The honest scope: this is the compiler itself working as a trustworthy, cached build input — the stage0 that larger native packages are compiled with. It is not a claim about any particular Rust application, and nothing graphical is implied by it. Both versions are on the protected list so retention and garbage collection never remove them.