android-ndk r10b

Previously the formula produced wrong directory structure. I've fixed it to be the same as when performing the following commands:
```
tar xf android-ndk32-r10b-darwin-x86_64.tar.bz2
tar xf android-ndk64-r10b-darwin-x86_64.tar.bz2
```
Again, please leave this as-is and let's try and fix the problem instead. Alternatively, make it `:recommended`