Setup the interface include directory that seems to not be setup
implicitly by CMake as it should be. This workaround is necessary to
ensure that we are able to build against this module.
This allows wiring up dependencies across the projects. In particular,
this is needed to get the generated VFS mapping in the Android build for
the explicit dependencies to work. The PCM emission does not receive the
required mapping and thus is unable to load the modulemaps for the build
of the PCM.
The install location of the APINotes is separate from the rest of the
overlay content. These are installed unlabelled by the OS (which is a
potential issue if there are conflicts with other OSes!). The swift
swift-driver properly locates the APINotes it appears, but the C++
swift-driver does not. Install the APINotes to a location that both will
function with.
The runtime mixes `swift` and `swift_static` SDK layouts when building
Swift code on Android. The overlay is always referenced in `swift` and
never from `swift_static`. Adjust the layout to match the driver.
