frozen modules are on by default in dev build

[gvanrossum]

BPO	47017
Nosy	@gvanrossum, @ericsnowcurrently

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-03-14.22:25:32.472>
labels = ['type-bug', '3.11']
title = 'frozen modules are on by default in dev build'
updated_at = <Date 2022-03-14.22:25:59.205>
user = 'https://github.com/gvanrossum'

bugs.python.org fields:

activity = <Date 2022-03-14.22:25:59.205>
actor = 'gvanrossum'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2022-03-14.22:25:32.472>
creator = 'gvanrossum'
dependencies = []
files = []
hgrepos = []
issue_num = 47017
keywords = []
message_count = 1.0
messages = ['415203']
nosy_count = 2.0
nosy_names = ['gvanrossum', 'eric.snow']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue47017'
versions = ['Python 3.11']

[gvanrossum]

At least on Windows and macOS, this repro shows that frozen modules are on in a dev build:

Mac:

~/cpython$ ./python.exe -c 'import os; print(os._exists.__code__)'
<code object _exists at 0x10dec7ee0, file "<frozen os>", line 41>

~/cpython$ ./python.exe -Xfrozen_modules=off -c 'import os; print(os._exists.__code__)'
<code object _exists at 0x10e851b50, file "/Users/guido/cpython/Lib/os.py", line 41>

On Windows, the same except use .\python.bat.