how to compile mingw-llvm-gcc in windows

Hello, llvm-dev.
thank you for your interest in my question.
Currently, I compiled simple c source code (hello.c) in lunux and windows, and I tried to simple test .
first case: hello.bc (compiled with “-emit-llvm” on windows) → lli.exe(linux).
second case: hello.bc (compiled with “-emit-llvm” on linux) → lli.exe(windows).
second case return good result.
but First case return error.
I want to modify and compile mingw-llvm-gcc by myself for such reasons.
Also I read several sentence about “how to cross-compilation form linux”, and Try it.
However, I could not succeed.
please, I would like to let me know “how to compile to the mingw-llvm-gcc” or further informations.
best regard.