#define + sizeof(...) fails to emit constant

Not sure if I'm missing a feature that's not supported yet but I hit issue and narrowed it down when trying to generate bindings for Lua.

Input C/C++ Header

#define SIZEOF_INT sizeof(int)

Bindgen Invokation

    bindgen::Builder::default()
        .header("test.h")
        .generate().unwrap()
        .write_to_file("src/out.rs").unwrap();

Actual Results

/* automatically generated by rust-bindgen */

Expected Results

RUST_LOG=bindgen Output

No logging emitted when I set env var

Full repro repo also exists here for easier debugging: https://github.com/vvanders/bindgen_repro

Reproduce the issue from the test.h header using the bindgen::Builder invocation shown, then inspect the generated src/out.rs. Compare the empty output with the expected SIZEOF_INT constant and use the RUST_LOG=bindgen result as a debugging check. Done means the sizeof macro is emitted as a constant in the generated bindings.