.der files are used only by the iOS platform for SSL pinning. This moves them out of the `platform/default/resources` directory and into `platform/ios/resources`. The make configuration for Android is updated so that it stops attempting to copy the files at all.
When adding new image resources, make sure that you've reduced the file size as much as possible using a tool such as: ImageOptim — https://imageoptim.com See also: https://github.com/mapbox/mapbox-gl-native/pull/2227