You could, for example, write a compiler in Python that generated native code (or LLVM bitcode to be passed to llc or whatever) via the LLVM API. Writing a compiler in Python vs. C/C++ would be a lot easier in a number of ways.

I'm not aware of any "production grade" compilers that do this, but no hard reason why not, I guess. Seems like it'd be nice for prototyping etc. if nothing else.