Minor tweak to `--no-binary` documentation to specify that when
enumerating packages, the colons are not needed. Additionally,
add an example to demonstrate building a wheel from source.
This section has caused a lot of user confusion since PEP 517/518. It seems that users are referring to this section for advice about how to deal with build time issues, which contains statements that do not hold true for build requirements.
The main setuptools PEP 517 backend is intended for
explicit usage in `pyproject.toml`, when the project
authors can ensure that their `setup.py` runs without
that directory being implicitly on `sys.path`.
For implicit usage, setuptools now offers a separate
legacy backend that more closely mimics direct
execution of the `setup.py` script.
This example did not make sense unless it was possible to install specify a
version of a package one installs referencing by the path (here: `.`).
A new example for the local installation with an extra has been added
instead.