.hsc/CPP Can't find headers.

I have an hsc file:

```hs
{-# LANGUAGE CPP #-}

module System.FUSE.Internal
-- TODO: explicit exports
where

#define FUSE_USE_VERSION 318

#include
```

I have my project setup fine, and running `cabal build` and `cabal repl` works. but for some reason I get these errors:

Start by reproducing the diagnostics for the shown .hsc file in Emacs, comparing them with the successful cabal build and cabal repl commands. Inspect how the mode handles CPP and the included fuse.h header. Done means the editor can resolve the header without reporting the shown errors while the existing build and REPL behavior remains intact.

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