Python may startup fails if the `home` variable in `pyvenv.cfg` is inaccurate

Bug report

Bug description:

The problem comes from getpath.py. When getpath.py cannot find STDLIB_LANDMARKS from executable_dir, it will set prefix to the PREFIX. If the directory set in PREFIX does not exist, an error occurs.

See details: https://github.com/python/cpython/blob/49f15d8667e4755876698a8daa13bab6acee5fa1/Modules/getpath.py#L590-L599

How to reproduce

# 1. build cpython with prefix
./configure --prefix=/home/xx/tmp/install_dir
make
make install

# 2. copy install_dir to another
cd /home/xx/tmp
cp -r ./install_dir/ ./copy_dir

# 3. create a symlink from copy_dir/python
ln -s ./copy_dir/bin/python3 ./pylink

# 4. delete original install_dir
rm -rf ./install_dir/

# 5. use python symlink to create a venv
./pylink -m venv ./bad_venv

# 6. failed to start!
./bad_venv/bin/python3

Error message

Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = './bad_venv/bin/python3'
  isolated = 0
  environment = 1
  user site = 1
  safe_path = 0
  import site = 1
  is in build tree = 0
  stdlib dir = '/home/xx/tmp/install_dir/lib/python3.12'
  sys._base_executable = '/home/xx/tmp/copy_dir/bin/python3.12'
  sys.base_prefix = '/home/xx/tmp/install_dir'
  sys.base_exec_prefix = '/home/xx/tmp/install_dir'
  sys.platlibdir = 'lib'
  sys.executable = '/home/xx/tmp/bad_venv/bin/python3'
  sys.prefix = '/home/xx/tmp/install_dir'
  sys.exec_prefix = '/home/xx/tmp/install_dir'
  sys.path = [
    '/home/xx/tmp/install_dir/lib/python312.zip',
    '/home/xx/tmp/install_dir/lib/python3.12',
    '/home/xx/tmp/install_dir/lib/python3.12/lib-dynload',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

We can find that sys._base_executable here is correct, but sys.base_prefix is ​​wrong.
We could configure base_prefix through the real interpreter path, which is used to search for libraries that Python depends on.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

• gh-127441

Bắt đầu với Modules/getpath.py quanh các dòng 590-599, sau đó chạy trên Linux quy trình tái hiện build, sao chép, symlink và venv đã được báo cáo. So sánh các giá trị sys._base_executable và sys.base_prefix thu được, đồng thời xem xét PR liên quan gh-127441. Được xem là hoàn tất khi trình thông dịch venv đã được di chuyển khởi động và có thể tải encodings mà không tham chiếu đến đường dẫn cài đặt đã bị xóa.