BLD: Ensure meson.build has the right version of Python

If `python3` is in the path, it might be picked up instead of the one
used to build. This is the case on GitHub actions, where cibuildwheel
seems to explicitly call the Python (3.11+) it wants, but `python3` is
in the hosted tool cache as an older version (3.9) that gets picked by
Meson. This matters because we need to run `setuptools_scm` to produce
the version, and it may not be installed in the `PATH`-based copy.

By specifying the version, Meson should skip the `PATH` option, and
choose its final fallback, the interpreter that it is itself running on.
While still not guaranteed to be correct everywhere, this should at
least work for CI.

Author: QuLogic

meson.build

@@ -1,7 +1,10 @@
 project(
   'matplotlib',
   'c', 'cpp',
-  version: run_command(find_program('python3'), '-m', 'setuptools_scm', check: true).stdout().strip(),
+  version: run_command(
+    # Also keep version in sync with pyproject.toml.
+    find_program('python3', version: '>= 3.11'),
+    '-m', 'setuptools_scm', check: true).stdout().strip(),
   # qt_editor backend is MIT
   # ResizeObserver at end of lib/matplotlib/backends/web_backend/js/mpl.js is CC0
   # Carlogo, STIX and Computer Modern is OFL

pyproject.toml

@@ -40,6 +40,7 @@ dependencies = [
     "pyparsing >= 3",
     "python-dateutil >= 2.7",
 ]
+# Also keep in sync with find_program of meson.build.
 requires-python = ">=3.11"
 
 [project.optional-dependencies]