ignore threads example on android

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

Author: sagudev

examples/threads.rs

@@ -3,6 +3,7 @@
 // This example demonstrates how to create a multithreaded OpenGL application using `surfman`.
 
 #![cfg(feature = "sm-raw-window-handle-06")]
+#![cfg(not(target_os = "android"))]
 
 use self::common::{ck, Buffer, Program, ResourceLoader, Shader, ShaderKind};