added support for fdk-aac [ci skip]
added support for fdk-aac [ci skip]

zebeurton/FFmpeg-iOS-build-script,zebeurton/FFmpeg-iOS-build-script,zebeurton/FFmpeg-iOS-build-script,zebeurton/FFmpeg-iOS-build-script,zebeurton/FFmpeg-iOS-build-script,zebeurton/FFmpeg-iOS-build-script