AFAIU the problem is that macOS has system python in
/Library/Frameworks/python.framework (or something like that) but homebrew
does not use that but installs its own python somewhere in /opt and meson
from homebrew uses that python but configure finds the system python which
does not have meson so it then downloads its own meson but that's too old
for macOS Sonoma
Correct (except s/downloads/installs/), basically --python/$PYTHON is the sole interpreter used to run *any* Python code during the QEMU build. The difference is that QEMU 8.1 would indeed download Meson, while QEMU 8.2 always uses the wheel that is shipped with QEMU. This change was done because the embedded Meson is intended to be a "known good" version that we (and pythondeps.toml) can point users to, in case a newer version from the distro has issues. Of course the other side of the coin is that an older version might not support new OSes as in this case.
The workaround below is not just a workaround but the intended solution if one wants to use the Meson and Sphinx packages from homebrew, and cannot modify the PATH to privilege homebrew's Python interpreter. In order to support Sonoma out of the box with the system Python, however, we can bump the shipped version of Meson to 1.2.x (and adjust pythondeps.toml).
Paolo
It should probably check for homebrew or macports
locations too or check for meson and get the python that's using. A
workaround apparently is to pass --python with the right path to
configure.