py.exe does not pass environment variable __COMPAT_LAYER to python.exe

[birdy-spb]

Bug report

Bug description:

C:\>set CustomVariable=CustomValue

C:\>py -3  -c "import os; print(os.environ.get('CustomVariable', 'not found'))"
CustomValue

C:\>python -c "import os; print(os.environ.get('CustomVariable', 'not found'))"
CustomValue

C:\>set __COMPAT_LAYER=Installer

C:\>python -c "import os; print(os.environ.get('__COMPAT_LAYER', 'not found'))"
Installer

C:\>py -3  -c "import os; print(os.environ.get('__COMPAT_LAYER', 'not found'))"
not found

Expected behavior:
Output for C:\>py -3 -c "import os; print(os.environ.get('__COMPAT_LAYER', 'not found'))" is Installer

Actual behavior:
Output for C:\>py -3 -c "import os; print(os.environ.get('__COMPAT_LAYER', 'not found'))" is not found

CPython versions tested on:

3.12

Operating systems tested on:

Windows