No need. For the Rust compiler, like most modern compilers, the list of systems it can produce binaries for is independent of which system it is running on. E

No need. For the Rust compiler, like most modern compilers, the list of systems it can produce binaries for is independent of which system it is running on. Either the compiler supports the instruction set and executable format used on Mac OS 9, or it doesn’t. If it does, then you could cross-compile Rust code for Mac OS 9 from any other supported system – including cross-compiling the compiler itself if desired. If it doesn’t, then it doesn’t, and even if you managed to run the compiler on Mac OS 9 (through a translation layer or otherwise), it would still only be able to produce code for its supported targets. An exception to this principle is the linker: the Rust compiler relies on an external linker, and it may happen that the standard linker for a system only runs on that system itself. This is true on modern macOS and Windows. In this case it’s impossible to cross-compile for the target normally (at least without using a nondefault linker such as LLD). But even in that case, it’s possible to separate the compile and link steps, so you could compile an object file on another system, copy the object file to the target system, and run the linker from there. That would be inconvenient but good enough for bootstrapping purposes, so a translation layer still wouldn’t really help.