Rect light LTC textures fail to load when cooking with bSharedLinearTextureEncoding enabled

When running a build with bSharedLinearTextureEncoding enabled, View.GGXLTCMatTexture and View.GGXLTCAmpTexture are pointing at the black texture fallback, which affects correctness of rect lighting.

This can be tracked back to FSystemTextures::InitializeEngineDependentTextures where IsTextureDataValid returns false due to the loaded UTexture2Ds' PrivatePlatformData having a null CPUCopy member.

It seems like any texture using ETextureAvailability::CPU would have this issue. A workaround is to skip the bit of FinalizeBuildSettingsForLayer that sets OutSettings.bAffectedBySharedLinearEncoding and OutSettings.Tiler if the texture uses ETextureAvailability::CPU

• Create a new project and add a rect light
• Add the following two lines to the project's DefaultEngine.ini config file:

[/Script/Engine.TextureEncodingProjectSettings]
bSharedLinearTextureEncoding=true

• Generate a cooked build for any target that supports bSharedLinearTextureEncoding