feat: 新增测试 runtime

apps/hello/src/main.rs

@@ -0,0 +1,9 @@
+fn main() {
+    println!("Hello from OpenWrt (ARMhf)!");
+    println!("System information (via /proc/version):");
+    if let Ok(version) = std::fs::read_to_string("/proc/version") {
+        println!("{}", version);
+    } else {
+        println!("Could not read /proc/version (running in simulation?)");
+    }
+}