refactor: Make eBPF build optional in packet-gateway build script

- Change eBPF build from required to optional with graceful fallback
- Add match statement to handle build success, failure, and missing cargo-build-bpf cases
- Add cargo warnings when eBPF build fails or cargo-build-bpf is not installed
- Remove panic on build failure to allow compilation without eBPF toolchain

apps/packet-gateway/build.rs

@@ -1,13 +1,22 @@
 use std::process::Command;
 
 fn main() {
-    // Build the eBPF program
+    // Try to build the eBPF program, but skip if cargo-build-bpf is not installed
     let status = Command::new("cargo")
         .args(&["build-bpf", "--release"])
-        .status()
-        .expect("Failed to execute cargo build-bpf");
+        .status();
 
-    if !status.success() {
-        panic!("Failed to build eBPF program");
+    match status {
+        Ok(status) if status.success() => {
+            // eBPF build succeeded
+        }
+        Ok(_) => {
+            // eBPF build failed, but continue without it
+            println!("cargo:warning=Failed to build eBPF program, continuing without it");
+        }
+        Err(_) => {
+            // cargo-build-bpf not installed, skip eBPF build
+            println!("cargo:warning=cargo-build-bpf not installed, skipping eBPF build");
+        }
     }
 }