Building the android apk on osx (case sensitive)

[Jason A. Donenfeld]

> ln: illegal option -- r
>
> usage: ln [-Ffhinsv] source_file [target_file]
>
>        ln [-Ffhinsv] source_file ... target_dir
>
>        link source_file target_file

The makefile uses options from coreutil's ln, which aren't available
on macOS. Use Linux to build the app. If Mac support in the build
system is really important to you and you have something useful you'd
like to contribute, I suppose I can futz with the makefile to use
simpler options to ln. Are you able to use Linux for development?