compileall doesn't recompile when invalidation mode changes even if timestamps match

Bug report

Bug description:

λ rm -rf __pycache__                                                                                                                            130 
λ python -m compileall x.py --invalidation-mode timestamp
Compiling 'x.py'...
λ python -m compileall x.py --invalidation-mode timestamp
λ python -m compileall x.py --invalidation-mode checked-hash

λ python
>>> import importlib.util
>>> with open("__pycache__/x.cpython-311.pyc", "rb") as f:
...     d = f.read()
... 
>>> d[:4]
b'\xa7\r\r\n'
>>> d[4:8]
b'\x00\x00\x00\x00'

λ rm -rf __pycache__
λ python -m compileall x.py --invalidation-mode checked-hash
Compiling 'x.py'...

λ python
>>> with open("__pycache__/x.cpython-311.pyc", "rb") as f:
...     d = f.read()
... 
>>> d[:4]
b'\xa7\r\r\n'
>>> d[4:8]
b'\x03\x00\x00\x00'

CPython versions tested on:

3.11

Operating systems tested on:

No response

使用 python -m compileall 通过 x.py 重现该行为，并检查 pycache 中生成的文件。从 compileall 命令入口开始，比较使用 timestamp 和 checked-hash 的重复运行。完成的标准是：更改失效模式会导致重新编译，或者以其他方式更新 pyc 头，即使 timestamp 匹配也是如此。