support pep517 builds - poetry install on Mac fails

On MacOS 14.3, python 3.11.7, in a project that needs python-snappy as a dependency of another library (in this case, localstack). After installing snappy with brew, the attempt to build python-snappy fails with:

```sh
• Installing python-snappy (0.6.1): Failed

ChefBuildError

Backend subprocess exited when trying to invoke build_wheel

/private/var/folders/s1/ls1zsdv57yj_hxx0ldh9h6jh0000gn/T/tmp2shjyr97/.venv/lib/python3.11/site-packages/setuptools/_distutils/dist.py:265: UserWarning: Unknown distribution option: 'cffi_modules'
warnings.warn(msg)
running bdist_wheel
running build
running build_py
creating build
creating build/lib.macosx-14-x86_64-cpython-311
creating build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/snappy.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/snappy_cffi.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/__init__.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/hadoop_snappy.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/snappy_formats.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/__main__.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
copying src/snappy/snappy_cffi_builder.py -> build/lib.macosx-14-x86_64-cpython-311/snappy
running build_ext
building 'snappy._snappy' extension
creating build/temp.macosx-14-x86_64-cpython-311
creating build/temp.macosx-14-x86_64-cpython-311/src
creating build/temp.macosx-14-x86_64-cpython-311/src/snappy
clang -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk -I/private/var/folders/s1/ls1zsdv57yj_hxx0ldh9h6jh0000gn/T/tmp2shjyr97/.venv/include -I/usr/local/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/include/python3.11 -c src/snappy/crc32c.c -o build/temp.macosx-14-x86_64-cpython-311/src/snappy/crc32c.o
clang -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk -I/private/var/folders/s1/ls1zsdv57yj_hxx0ldh9h6jh0000gn/T/tmp2shjyr97/.venv/include -I/usr/local/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/include/python3.11 -c src/snappy/snappymodule.cc -o build/temp.macosx-14-x86_64-cpython-311/src/snappy/snappymodule.o
src/snappy/snappymodule.cc:33:10: fatal error: 'snappy-c.h' file not found
#include
^~~~~~~~~~~~
1 error generated.
error: command '/usr/bin/clang' failed with exit code 1

at /usr/local/lib/python3.10/site-packages/poetry/installation/chef.py:164 in _prepare
160│
161│ error = ChefBuildError("\n\n".join(message_parts))
162│
163│ if error is not None:
→ 164│ raise error from None
165│
166│ return path
167│
168│ def _prepare_sdist(self, archive: Path, destination: Path | None = None) -> Path:

Note: This error originates from the build backend, and is likely not a problem with poetry but with python-snappy (0.6.1) not supporting PEP 517 builds. You can verify this by running 'pip wheel --no-cache-dir --use-pep517 "python-snappy (==0.6.1)"'.

```

I can manually cause python-snappy to be built with pip, outside of the pep517 / poetry infrastructure, with a workaround command such as the one in the README, e.g. for me:

```sh
CPPFLAGS="-I$(brew --prefix)/include -L$(brew --prefix)/lib" poetry run pip install python-snappy
```

This works but is really frustrating - I see there are quite a lot of MacOS-related build issues already, and am trying to avoid raising a duplicate.

Obviously I'd prefer that the build script just worked entirely, but even if I had to manually set `CPPFLAGS` it would be a big improvement if python-snappy were to support PEP 517 builds directly.