Fix build script deadlock in release mode

build.rs

@@ -4,16 +4,21 @@ use std::process::Command;
 
 fn main() {
     println!("cargo:rerun-if-changed=client");
-    build_client();
-
     let out_dir = env::var("OUT_DIR").unwrap();
+    let client_bin = build_client(&out_dir);
+
     setup_nyx(&out_dir);
 
-    create_nyx_workdir(&out_dir);
+    create_nyx_workdir(&out_dir, &client_bin);
 }
 
 #[track_caller]
 fn shell(cwd: impl AsRef<Path>, command_string: &str) {
+    println!(
+        "cargo:warning=Running ({}) {command_string}",
+        cwd.as_ref().display()
+    );
+
     let cwd = cwd.as_ref();
     let mut parts = command_string.split(" ");
     let command_name = parts.next().unwrap();
@@ -34,8 +39,14 @@ fn shell(cwd: impl AsRef<Path>, command_string: &str) {
     }
 }
 
-fn build_client() {
-    shell("client", "cargo build --release");
+/// Builds the client and returns the path to its binary
+fn build_client(out_dir: &str) -> String {
+    // Change the target dir to avoid a cargo target dir deadlock
+    shell(
+        "client",
+        &format!("cargo build --release --target-dir {out_dir}/client_target"),
+    );
+    format!("{out_dir}/client_target/release/client")
 }
 
 /// Downloads and compiles qemu-nyx and packer and compiles them for the current architecture
@@ -71,13 +82,12 @@ fn setup_nyx(out_dir: &str) {
     }
 }
 
-fn create_nyx_workdir(out_dir: &str) {
+fn create_nyx_workdir(out_dir: &str, client_bin: &str) {
     // Create the directory and move required binaries to it
-    let repository_root = env::var("CARGO_MANIFEST_DIR").unwrap();
     shell(
         out_dir,
         &format!(
-            "python3 packer/packer/nyx_packer.py {repository_root}/target/release/client build afl processor_trace --fast_reload_mode --purge"
+            "python3 packer/packer/nyx_packer.py {client_bin} build afl processor_trace --fast_reload_mode --purge"
         ),
     );