[jjpe]

This is not as much as a problem as you believe. Rust is perfectly capable of making objects that have a C API and ABI precisely for this reason, and the most popular distros only work with supported compile targets anyway. That said, a distro like Debian might indeed encounter some issues at this time for the less prominent platforms eg MIPS or PowerPC based chips. That shouldn't prevent Debian from including Rust altogether though, they merely should exclude it on those less or even unsupported platforms.