The subtarget to build. (optional)
For some BuildTargets the behaviour of a build can be influenced by using this field.
The supported values are based on target-specific enums, for example MobileTextureSubtarget, XboxBuildSubtarget.
The subtarget can be assigned using the build settings UI. To build with the current build settings, the BuildAssetBundlesParameters.targetPlatform field should be left unassigned (e.g. with the value 0).
Additional resources: EditorUserBuildSettings.standaloneBuildSubtarget, EditorUserBuildSettings.androidBuildSubtarget, EditorUserBuildSettings.webGLBuildSubtarget, EditorUserBuildSettings.ps4BuildSubtarget.