Only for very simple systems. Many are complicated which produce artifacts that are executed to produce other artifacts (which are also compiled). As arbitrar

Only for very simple systems. Many are complicated which produce artifacts that are executed to produce other artifacts (which are also compiled). As arbitrary binaries are executed during the build, and the correctness may depend on native execution, this is far from as trivial as you might think. Have you ever compiled Emacs (at least in its 18 version)? Building under QEMU is obvious, however the native hardware is actually faster.