The documentation of
- https://docs.python.org/3.11/using/configure.html#envvar-CFLAGS
- https://docs.python.org/3.11/using/configure.html#envvar-CFLAGS_NODIST
- https://docs.python.org/3.11/using/configure.html#envvar-LDFLAGS
- https://docs.python.org/3.11/using/configure.html#envvar-LDFLAGS_NODIST
should explain more clearly that flags such as `-I`, `-L`, etc. and strict compiler flags such as `-Werror...` should not be put into `CFLAGS`, `LDFLAGS`, or it will make the resulting Python unusable for compiling user packages with extension modules via `distutils` and `setuptools`.

Various downstream packagers have provided misconfigured Pythons:
- Homebrew (https://trac.sagemath.org/ticket/31132, https://github.com/Homebrew/homebrew-core/pull/68528, resolved)
- Cygwin (https://trac.sagemath.org/ticket/33078, https://cygwin.com/pipermail/cygwin/2021-December/250302.html, resolved in a proposed package update)
- pyenv (https://trac.sagemath.org/ticket/32531, https://github.com/pyenv/pyenv/issues/2204, open)

So this appears to be a documentation / user education issue in CPython.