Py: Fix build.rs on CI

Author: w1th0utnam3

pysplashsurf/build.rs

@@ -1,11 +1,9 @@
 fn main() {
+    // Required to run cargo check or stub gen outside of maturing build
     if std::env::var_os("CARGO_CFG_TARGET_OS=macos").is_some() {
-        println!(
-            "cargo:rustc-link-arg=-Wl,-rpath,{}",
-            pyo3_build_config::get()
-                .lib_dir
-                .clone()
-                .expect("Python lib dir not found")
-        );
+        pyo3_build_config::get()
+            .lib_dir
+            .clone()
+            .map(|lib_dir| println!("cargo:rustc-link-arg=-Wl,-rpath,{}", lib_dir));
     }
 }