Enable gles2 canvas fast path on the Raspberry Pi
Created by: efornara
This allows the Raspberry Pi use the gles2 canvas fast path out of the box.
Not the perfect way to autodetect the Raspberry Pi, but I reckon that this is a fairly non-invasive method and I believe the Raspberry Pi is the most popular "desktop" (i.e. GLES_OVER_GL) running on ARM anyway.
__aarch64__
is not strictly needed, but some people are running 64 bits distro, and it would be a shame to leave them out.
See https://github.com/godotengine/godot/issues/2671 and https://github.com/godotengine/godot/issues/24466