Add note on building for Android

[skip CI]

Author: SaschaWillems

README.md

@@ -39,10 +39,13 @@ qmake5 -config release DEFINES+=WAYLAND
 
 Note: Do not enable both flags simultaneously.
 
+## Android
+
+The Android apk needs to be built from Qt Creator and requires Android SDK and Android NDK. Note that Qt 5.15.2 will not work with recent NDKs, you must install and select NDK 21.x under Settings -> Devices -> Android.
 
 # Releases
 Current releases for all platforms will be provided on a regular basis at [vulkan.gpuinfo.org/download.php](https://vulkan.gpuinfo.org/download.php).
 
 # Dependencies
 - [Vulkan SDK](https://vulkan.lunarg.com/)
-- [Qt 5.15](https://www.qt.io/developers/) - Older versions may not work due to missing functionality
+- [Qt 5.15.2](https://www.qt.io/developers/) - Older versions may not work due to missing functionality