build(feat): Support pyenv/Python installation on Big Sur

[armenzg]

Installing Python via pyenv on Big Sur for older Python versions requires:

• Setting LDFLAGS for zlib (Add LDFLAGS for zlib on macOS >= 1100 pyenv/pyenv#1711)
• Patching the source code

Once a new release of pyenv is released and we use a newer Python 3 version
we will not need all these hacks and all Mac versions will be able to use
the same code paths.

Fixes #22497

[joshuarli]

I'll try this out tonight.

[armenzg]

@joshuarli Hi Josh, please let me know if you will be able to give it a try or if I should ask for another person that has Big Sur already installed. Thanks!

[joshuarli]

Okay, removing my 3.6.10 and starting out with a slightly outdated pyenv (pyenv@943015ebb2ee2ec3b249e1177d8b8531d0ee3960) on Big Sur. However, it does include the proper zlib ldflags patch.

python-build: use [email protected] from homebrew
python-build: use readline from homebrew
Downloading Python-3.6.10.tar.xz...
-> https://www.python.org/ftp/python/3.6.10/Python-3.6.10.tar.xz
Installing Python-3.6.10...
python-build: use readline from homebrew
python-build: use zlib from xcode sdk

BUILD FAILED (OS X 11.0.1 using python-build 1.2.21-1-g943015eb)

Inspect or clean up the working tree at /var/folders/09/m6yjxzfj5s1gyt1_vkwhy6ch0000gn/T/python-build.20201211115124.4300
Results logged to /var/folders/09/m6yjxzfj5s1gyt1_vkwhy6ch0000gn/T/python-build.20201211115124.4300.log

Last 10 log lines:
                   ^
./Modules/posixmodule.c:8130:12: note: forward declaration of 'struct sf_hdtr'
    struct sf_hdtr sf;
           ^
./Modules/posixmodule.c:8210:15: error: implicit declaration of function 'sendfile' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        ret = sendfile(in, out, offset, &sbytes, &sf, flags);
              ^
2 errors generated.
make: *** [Modules/posixmodule.o] Error 1
make: *** Waiting for unfinished jobs....

Tried make setup-pyenv, same failure.

Edit: never mind, I forgot to checkout the branch, haha. I see python's configure stuff being patched and it works!

[joshuarli]

Great work, thanks for taking care of this. You have my blessing.

I expect we can only totally remove all this once Sentry's on 3.8, I have no problems compiling 3.8.6 OOTB.

[armenzg]

Thank you Josh for testing this out!