Can I build Unity Android and iOS plugins as DLLs? as in compile all the .jars, .mm and the .cs together as 1 DLL?

Similar to what Parse did for their Unity Plugin. How did they compile everything into just one dll file?

Also does a Unity build for iOS compile dll files that are located in the Plugins/Android folder, and vice versa?

Because when I build an iOS project with a DLL that references any Java code using AndroidJavaObject, it fails (Cross compilation job .dll failed.). DLLs, as far as I know, can't use conditional compilations, so I split my DLL into two, one for iOS and one for Android, but I'm hoping that when I build for iOS it will not try to compile the Android version, and vice versa.

I'm sorry if there are two questions in this post, but they're related...