WIDL compiler incompatibilities with Windows SDK
I attempted to compile the IDL files distributed in https://github.com/microsoft/win32metadata/tree/master/generation/WinSDK/RecompiledIdlHeaders using the latest (7.0.1-rc.1) version of the Wine IDL compiler, called WIDL. Unlike Microsoft's MIDL compiler which ships with Visual Studio, WIDL is open source.
More importantly, WIDL contains patches to generated header files that make e.g. COM calling conventions compatible with mingw-w64 and clang when targetting GNU ABI.