csfml 2.0 (new formula)

CSFML are the C bindings to the SFML library (already present in
Homebrew).
I am not sure how to do that.  My problem is that the `CMakeLists.txt` file in the *subdirectory* `src/SFML` needs to be able to find the `FindSFML.cmake` from the installation of the `sfml` formula.  This file is found at `#{HOMEBREW_PREFIX}/share/SFML/cmake/Modules/`.
I tried doing

    cmake -DCMAKE_MODULE_PATH=#{HOMEBREW_PREFIX}/share/SFML/cmake/Modules/ .

at the root of the source directory, but the variable `CMAKE_MODULE_PATH` does *not* seem to be passed to the subdirectory `src/SFML`, so `cmake` fails when processing `src/SFML/CMakeLists.txt`.

Any ideas?