Fix c-wrapper-crate template

Author: xxuejie

c-wrapper-crate/src/lib.rs

@@ -6,6 +6,11 @@ extern "C" {
     fn bar() -> core::ffi::c_int;
 }
 
+#[cfg(not(target_arch = "riscv64"))]
+unsafe fn bar() -> core::ffi::c_int {
+    unreachable!()
+}
+
 pub fn value() -> u32 {
     (unsafe { bar() }) as u32
 }