bin: add wrapper to run scripts in a python venv

This isolates the script environment from the rest of the machine,
avoiding missing/incompatible dependencies and avoiding polluting the
rest of the machine with python packages.

Signed-off-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24367>

bin/python-venv.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+set -eu
+
+readonly requirements_file=$1
+shift
+
+venv_dir="$(dirname "$requirements_file")"/.venv
+readonly venv_dir
+readonly venv_req=$venv_dir/requirements.txt
+
+if ! [ -r "$venv_dir/bin/activate" ]
+then
+  echo "Creating Python environment..."
+  python -m venv "$venv_dir"
+fi
+
+# shellcheck disable=1091
+source "$venv_dir/bin/activate"
+
+if ! cmp --quiet "$requirements_file" "$venv_req"
+then
+  echo "$(realpath --relative-to="$PWD" "$requirements_file") has changed, re-installing..."
+  pip --disable-pip-version-check install --requirement "$requirements_file"
+  cp "$requirements_file" "$venv_req"
+fi
+
+python "$@"