The CLR model has always had support for instruction to support the C/C++ language, compile plugins or similar once and load/run on multiple platforms should be possible.

However, iirc there might've been some issues with libraries making the cl /clr code unportable (don't quote me on that though), starting from scratch might yield a better result if one just wants to run C code everywhere.

Note that Microsoft "cl /clr" also does this. It's a bit of a niche use case.