MANIFEST.in will now include pyproject.toml

[zwimer]

This change should ensure that even if your CI is older, the generated sdist z3 publishes to pypi should include pyproject.toml. This should ensure that pyproject.toml is distributed with the pip sdist, thus whenever pip builds the z3 wheel it should honor build dependencies if the user's software is new enough. If their software is too outdated this just adds a couple extra bytes to the size of the package but should otherwise be ignored.

Tested via:

FROM alpine
RUN apk add --no-cache make g++ python3 py3-pip git
RUN pip install --upgrade pip

# Clone
RUN git clone --depth 1 https://github.com/Z3Prover/z3 /z3
WORKDIR /z3/src/api/python

# Add change
RUN echo "include pyproject.toml" >> MANIFEST.in

# Gen sdist
RUN python3 setup.py sdist
WORKDIR dist

# Build pip install from sdist to mimic pip install from pypy sdist
RUN tar -xvf *; rm -rf *.gz; mv * dir
WORKDIR dir
RUN pip install .