meson: Run the test with Python

This is a patch from me and a patch from Mathieu Bridon squashed
together.

Signed-off-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Mathieu Bridon <bochecha@daitauha.fr>
(cherry picked from commit e1568656)
[Andres Gomez: applied cleanly but backported as suggested by Emil]
Signed-off-by: Andres Gomez <agomez@igalia.com>