Updated Working for Android (on Linux) (markdown)

Working-for-Android-(on-Linux).md

@@ -1,5 +1,7 @@
 This guide shows you how to set up and build a raylib project for Android on Linux. This was tested on Ubuntu 21.10 (64-bit only) and Android 10. Generated APK files will run on Android 6 and up.
 
+This guide is based on [gxbuild](https://github.com/gtrxAC/gxbuild), a simple shell script based build system that can build for Windows, Linux, Web and Android.
+
 # Setup
 
 ## Directory setup