Allows the use of OAuth credentials set up via environment variables
(as used on CI) without the need for extra plumbing via build scripts.
Also sets GPU_PRIORITY_VAL via preset on Windows.
Camera Extensions require specific entitlements for the hosting app,
which also require a provisioning profile. To avoid breaking local
builds that do not require the camera extension, an additional
entitlements file that will not trigger the provisioning profile
requirement will be used if the virtualcam (but not the Camera
Extension) is configured.
