Fix bug when contract not has features: native-simulatorg (#129)

* Fix bug when contract not has features: native-simulatorg

Author: joii2020

contracts/exec-callee/src/entry.rs

@@ -5,6 +5,7 @@ use core::result::Result;
 // https://nervosnetwork.github.io/ckb-std/riscv64imac-unknown-none-elf/doc/ckb_std/index.html
 
 use crate::error::Error;
+extern crate alloc;
 
 pub fn main() -> Result<(), Error> {
     let argv = ckb_std::env::argv();

src/debug.rs

@@ -32,15 +32,11 @@
 #[macro_export]
 macro_rules! debug {
     ($fmt:literal) => {
-        #[cfg(all(debug_assertions, feature = "native-simulator"))]
-        $crate::syscalls::debug(format!($fmt));
-        #[cfg(all(debug_assertions, not(feature = "native-simulator")))]
+        #[cfg(debug_assertions)]
         $crate::syscalls::debug(alloc::format!($fmt));
     };
     ($fmt:literal, $($args:expr),+) => {
-        #[cfg(all(debug_assertions, feature = "native-simulator"))]
-        $crate::syscalls::debug(format!($fmt, $($args), +));
-        #[cfg(all(debug_assertions, not(feature = "native-simulator")))]
+        #[cfg(debug_assertions)]
         $crate::syscalls::debug(alloc::format!($fmt, $($args), +));
     };
 }