move gnu warning to build script

packages/desktop/build.rs

@@ -0,0 +1,9 @@
+fn main() {
+    // WARN about wry support on windows gnu targets. GNU windows targets don't work well in wry currently
+    if std::env::var("CARGO_CFG_WINDOWS").is_ok()
+        && std::env::var("CARGO_CFG_TARGET_ENV").unwrap() == "gnu"
+        && !cfg!(feature = "gnu")
+    {
+        println!("cargo:warning=GNU windows targets have some limitations within Wry. Using the MSVC windows toolchain is recommended. If you would like to use continue using GNU, you can read https://github.com/wravery/webview2-rs#cross-compilation and disable this warning by adding the gnu feature to dioxus-desktop in your Cargo.toml")
+    }
+}