Fix Rust edition 2024 compatibility

This adds `unsafe` to all `extern "C" { ... }` generated blocks to account for edition 2024 requirements.

Author: daxpedda

crates/backend/src/codegen.rs

@@ -276,7 +276,7 @@ impl ToTokens for ast::Struct {
 
                     #[link(wasm_import_module = "__wbindgen_placeholder__")]
                     #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
-                    extern "C" {
+                    unsafe extern "C" {
                         fn #new_fn(ptr: u32) -> u32;
                     }
 
@@ -382,7 +382,7 @@ impl ToTokens for ast::Struct {
 
                     #[link(wasm_import_module = "__wbindgen_placeholder__")]
                     #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
-                    extern "C" {
+                    unsafe extern "C" {
                         fn #unwrap_fn(ptr: u32) -> u32;
                     }
 
@@ -1067,7 +1067,7 @@ impl ToTokens for ast::ImportType {
                     fn instanceof(val: &JsValue) -> bool {
                         #[link(wasm_import_module = "__wbindgen_placeholder__")]
                         #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
-                        extern "C" {
+                        unsafe extern "C" {
                             fn #instanceof_shim(val: u32) -> u32;
                         }
                         #[cfg(not(all(target_arch = "wasm32", target_os = "unknown")))]
@@ -1762,7 +1762,7 @@ fn static_init(wasm_bindgen: &syn::Path, ty: &syn::Type, shim_name: &Ident) -> T
     quote! {
         #[link(wasm_import_module = "__wbindgen_placeholder__")]
         #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
-        extern "C" {
+        unsafe extern "C" {
             fn #shim_name() -> #abi_ret;
         }
 
@@ -1843,7 +1843,7 @@ fn extern_fn(
         #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
         #(#attrs)*
         #[link(wasm_import_module = "__wbindgen_placeholder__")]
-        extern "C" {
+        unsafe extern "C" {
             fn #import_name(#(#abi_arguments),*) -> #abi_ret;
         }