- Re-enable renderdiff test.
- Cache the mesa directory so that we're not spending time pulling
and compiling it.
- Move python prereqs into the script and use venv.
PPM does not store alpha channel, but TIFF does. We add a method
to export RGBA to a TIFF file without compression.
We add the corresponding options to gltf_viewer and
AutomationEngine.
The default export format for both gltf_viewer and AutomationEngine
is now TIFF.
We use Mesa's gallium swrast to render as the driver with
Filament's backend set to GL. We provide a few scripts to parse
the tests (as jsons) and run gltf_viewer to produce the rendering.
