Distribute pre-built cross-compiled runtimes in ponyc releases #4968
Description
Cross-compilation to Linux targets via embedded LLD (Phase 2, PR #4964) works well, but users who install ponyc via ponyup currently have no way to get the cross-compiled runtime libraries without cloning the ponyc source and running the full build pipeline (make libs + make cross-libponyrt). This is a significant barrier since make libs builds LLVM from source.
We should include pre-built cross-compiled runtimes (libponyrt + CRT objects) for our CI-tested cross targets in the ponyc release artifacts. This would let ponyup users cross-compile by installing target sysroot packages and pointing PONYPATH at the bundled runtime — no source build required.
Targets to include:
- riscv64-unknown-linux-gnu
- arm-unknown-linux-gnueabi
- arm-unknown-linux-gnueabihf