Change shared library installation directory from /lib/python3.10/site-packages/ to /usr/lib.
#2686 and this PR improve how we load shared libraries. The future goal
of these PRs is to load shared libraries on demand, instead of pre-loading
all shared libraries, which will reduce initial package load time.
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).
Gyeongjae Choi