sphinx-build -M not listed in sphinx-build --help

[deliciouslytyped]

Describe the bug

This is a followup on #6603 .
The -M flag still isn't listed in --help, though it is documented in https://www.sphinx-doc.org/en/master/man/sphinx-build.html .

How to Reproduce

Just run sphinx-build --help

Environment Information

Platform:              linux; (Linux-6.1.46-x86_64-with-glibc2.39)
Python version:        3.12.4 (main, Jun  6 2024, 18:26:44) [GCC 13.3.0])
Python implementation: CPython
Sphinx version:        7.4.6
Docutils version:      0.21.2
Jinja2 version:        3.1.4
Pygments version:      2.18.0

Sphinx extensions

No response

Additional context

Tangential xref for my usecase;
sphinx-doc/sphinx-autobuild#151
sphinx-doc/sphinx-autobuild#64

[AA-Turner]

PR welcome!

A