[delta_p_delta_x]

There are some pretty useful abstractions and libraries that MinGW doesn't work with. Biggest example is the WIL[1], which Windows kernel programmers use and is a massive improvement in ergonomics and safety when writing native Windows platform code.

[1]: https://github.com/microsoft/wil

[vitaminCPP]

I fail to see why this would not work with gcc if it works with clang. The runtime?

[delta_p_delta_x]

'MinGW' is not GCC; it's an ABI, and from the developer perspective it is also the headers and the libraries. You can have GCC MinGW, Clang MinGW, Rust MinGW, Zig MinGW, C# AOT MinGW.

To answer your question, the headers.