The bootstrap.pypa.io URLs for pip installation changed.

Added aarch64 for Linux in anaconda_architecture()

Added aarch64 for Linux in anaconda_architecture()

fixes #1805

Fix pyenv to continue to support legacy Python builds despite the fact that `get-pip` has dropped support for Python 2 as discussed in pypa/get-pip#87

* Update python-build with arm64 architecture

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

* Remove Ruby references from python-build

* restore fix_directory_permissions

This PR fixes (currently harmless) warning on macOS when homebrew is *not* installed.

- [ ] Test case (required?)

For example:

```sh
wadkar$ pyenv install 3.8.2
/Users/wadkar/.pyenv/plugins/python-build/bin/python-build: line 1541: brew: command not found
/Users/wadkar/.pyenv/plugins/python-build/bin/python-build: line 1541: brew: command not found
Installing openssl-1.1.0j...
Installed openssl-1.1.0j to /Users/wadkar/.pyenv/versions/3.8.2

Installing readline-8.0...
Installed readline-8.0 to /Users/wadkar/.pyenv/versions/3.8.2

Installing Python-3.8.2...
python-build: use zlib from xcode sdk
Installed Python-3.8.2 to /Users/wadkar/.pyenv/versions/3.8.2
```

The official pypy builds should now be portable on linux.
Also add aarch64 builds.

fixes #1219, #1333

This reverts commit 070e1c859fb2584c3dbe0a6fbe58cbc80938654e, reversing
changes made to 3faeda67bb.

previously, it was not possibly to compile a python with homebrew
openssl 1.1 because the code always queried "openssl" and ignored
"openssl@1.1".

now, if 1.1 is installed, it is used to compile python and only
if it is not, 1.0 is checked and used.

All scripts in libexec/ (excluding pyenv) are called through pyenv,
therefore the shebang lines are not necessary. On some systems this
provides a measurable increase in performance of the shell prompt.

Related to pyenv/pyenv-virtualenv#259

The script in `Tools/gdb/libpython.py` has helper functions for
debugging Python processes under gdb. When installed to `{exe}-gdb.py`
it will automatically be loaded by gdb assuming it is in the safe path.

gdb resolves all symlinks, so having the single script is sufficient
regardless of how Python is invoked.

Since it is usually only included as part of a dbg/dev package, this
file is intentionally excluded from install by the CPython build
scripts. Like the packaging with EPEL/Debian, we opt to manually copy
it after the build/install.

To ensure this file gets picked up it is enough for users to put this in
their `~/.gdbinit`:

```
add-auto-load-safe-path ~/.pyenv
```

Fixes #1190.

Ref (abs_dirname in bats): https://github.com/sstephenson/bats/pull/224
Ref: https://github.com/rbenv/rbenv/pull/868

Fixes https://github.com/pyenv/pyenv/issues/580

reapplying 4ebba7cd5f , which is (accidently?) reverted by fc90785f75

Manage `GET_PIP_URL` value at single place for readability.

Push 3.7-dev to `3.7` branch

closes #1061