Re: nim android tutorial

[treeform]

Also see my: 
[https://forum.nim-lang.org/t/5197](https://forum.nim-lang.org/t/5197)

And manual: 
[https://nim-lang.org/docs/nimc.html#cross-compilation-for-android](https://nim-lang.org/docs/nimc.html#cross-compilation-for-android)