Worker: run settings['blender_cmd'] through shlex

This allows for more complex Blender commands. Before this commit, the
setting could only point to an executable; now it is also possible to
provide extra CLI arguments to Blender.

packages/flamenco-worker-python/flamenco_worker/runner.py

@@ -422,8 +422,10 @@ class BlenderRenderCommand(AbstractSubprocessCommand):
         return None
 
     async def execute(self, settings: dict):
-        cmd = [
-            settings['blender_cmd'],
+        import shlex
+
+        cmd = shlex.split(settings['blender_cmd'])
+        cmd += [
             '--enable-autoexec',
             '-noaudio',
             '--background',