BUG: meson.build runs gitversion.py with the wrong Python interpreter #24514
Description
Describe the issue:
meson.build expects that python in the PATH is a working Python 3; that's not a good assumption.
Given that meson is run via meson_python, the Python in sys.executable should be used instead of leaving it to external circumstances. Note in particular that venvs created by python -m venv have python3 executables but not python executables.
This is on numpy 1.26.0b1 with #24503 as a patch.
I see this on ubuntu-focal, where there's no /usr/bin/python. https://github.com/mkoeppe/sage/actions/runs/5954216252/job/16159923132#step:8:2353
[numpy-1.26.0b1] The Meson build system
[numpy-1.26.0b1] Version: 1.2.99
[numpy-1.26.0b1] Source dir: /sage/local/var/lib/sage/venv-python3.11.1/var/tmp/sage/build/numpy-1.26.0b1/src
[numpy-1.26.0b1] Build dir: /sage/local/var/lib/sage/venv-python3.11.1/var/tmp/sage/build/numpy-1.26.0b1/src/.mesonpy-q4xlebps/build
[numpy-1.26.0b1] Build type: native build
[numpy-1.26.0b1]
[numpy-1.26.0b1] ../../meson.build:4:11: ERROR: Program or command 'python' not found or not executable
[numpy-1.26.0b1]
I also see this on ubuntu-xenial-toolchain-gcc_9, where /usr/bin/python is an unusable Python 2. https://github.com/mkoeppe/sage/actions/runs/5954216252/job/16159922994#step:11:1438
The Meson build system
Version: 1.2.99
Source dir: /sage/local/var/lib/sage/venv-python3.11.1/var/tmp/sage/build/numpy-1.26.0b1/src
Build dir: /sage/local/var/lib/sage/venv-python3.11.1/var/tmp/sage/build/numpy-1.26.0b1/src/.mesonpy-1mht6y46/build
Build type: native build
../../meson.build:4:11: ERROR: Command `/usr/bin/python numpy/_build_utils/gitversion.py` failed with status 1.
Reproduce the code example:
$ pip install .Error message:
../../meson.build:4:11: ERROR: Program or command 'python' not found or not executableRuntime information:
N/A