feat: Add build script for eBPF program compilation with cargo build-bpf integration

- Add build.rs with Command execution for cargo build-bpf --release
- Add status check with panic on build failure for eBPF program compilation

apps/packet-gateway/build.rs

@@ -0,0 +1,13 @@
+use std::process::Command;
+
+fn main() {
+    // Build the eBPF program
+    let status = Command::new("cargo")
+        .args(&["build-bpf", "--release"])
+        .status()
+        .expect("Failed to execute cargo build-bpf");
+
+    if !status.success() {
+        panic!("Failed to build eBPF program");
+    }
+}