target 'SDK' has invalid header layout: umbrella header found at '.../Sources/SDK/include/SDK.h', but directories exist next to it: .../Sources/SDK/include/cpp, /.../Sources/SDK/include/hx; consider removing them
But these directories contain the headers that my umbrella header is including. Am I required to flatten the hierarchy in order to use an umbrella header for a C++ target with SPM?
