dist is both more accurate (the 'build' directory is normally where you do the build,
and normally consists of intermediate build artifacts no one cares about). dist also
occurs less frequently in the code base: after this change \bbuild\b has 466 matches,
whereas \bdist\b has 101 matches. build has 1072 matches whereas dist has 362.
We are pushing pyodide_build to PyPI as a Python package, but for now,
installing pyodide_build from PyPI (i.e. pip install pyodide_build`) is almost
useless because:
there are bunch of hard-coded paths (e.g. Path(__file__).parents[2]),
its dependencies are not specified in setup.cfg.
This PR is for mitigating this situation by removing hard-coded paths and
adding tests, and is also a preparation for our new CLI
(https://github.com/pyodide/pyodide/issues/1977).
Roman Yurchak