more general installation readme instructions

corrected fish shell command

Added Miniforge 3

OS X arm64 will be installed with Python 3.9 only. Other versions bundled with python 3.8. Miniforge does not have as wide a choice of python versions as miniconda.
The Python version is specific only to the base environment.

Add pypy3.7

Add PyPy 3.7-7.3.2 (binary distribution)

Add PyPy 3.7-7.3.2 (source distribution)

Use verify_py38 for anaconda3-2020.07

Create pypy3.7-7.3.3

Create pypy3.7-7.3.3-src

Bump version to  4.9.2-5

* Update python-build with arm64 architecture

Per the release notes the installer and base environment (which I assume
we'd be verifying here, if anything) is Python 3.8.

Added support for Anaconda 2020.11

Added Miniforge3-4.9.2 support for all platforms, including arm64 in macOS for Apple M1 SoC

Add CPython 3.8.7

* Add GraalPython 20.3

* Update graalpython repository URLs

This prevents people from jumping the gun and trying to install a python version right after brew install.

* Dockerfile for testing python builds

* README: document docker usage

* Finish docker

dockerignore file, specify ephemeral nature of containers.

* Move docs for docker usage to python-build README

Add LDFLAGS for Xcode SDK zlib on macOS >= 1100 to resolve build issues on Big Sur.

... which is caused by `realpath.dylib` containing illegal UTF-8 byte sequence, and `LC_CTYPE` won't take effect if `LC_ALL` happens to be set to something other than `C`.

This commit fixes issue pyenv/pyenv#1454.

Ref: https://stackoverflow.com/a/23584470

PyPy has now only one development tip, `default`,
others are version-line-specific maintenance branches.
The py3k branch has been closed in 2016.
As such, a separate pypy3-dev entry no longer makes sense.

exclude bin files from coreutils

* Find working PyPy links in downloads.python.org
* Use portable-pypy links from softwareheritage.org