message: Fix missing NUL for setenv
diff: @@ -857,6 +857,7 @@ unsafe fn copy_kv(existing: *mut c_char, key: *const c_char, value: *const c_cha
  core::ptr::copy_nonoverlapping(key, existing, key_len);
  core::ptr::write(existing.add(key_len), b'=' as c_char);
  core::ptr::copy_nonoverlapping(value, existing.add(key_len + 1), value_len);
  + core::ptr::write(existing.add(key_len + 1 + value_len), 0);
  }
  #[no_mangle]
  @@ -878,15 +879,17 @@ pub unsafe extern "C" fn setenv(
  if existing_len >= value_len {
  // Reuse existing element's allocation
  core::ptr::copy_nonoverlapping(value, existing, value_len);
  + //TODO: fill to end with zeroes
  + core::ptr::write(existing.add(value_len), 0);
  } else {
  // Reuse platform::environ slot, but allocate a new pointer.
  - let mut ptr = platform::alloc(key_len as usize + 1 + value_len as usize) as *mut c_char;
  + let mut ptr = platform::alloc(key_len as usize + 1 + value_len as usize + 1) as *mut c_char;
  copy_kv(ptr, key, value, key_len, value_len);
  platform::environ.add(i).write(ptr);
  }
  } else {
  // Expand platform::environ and allocate a new pointer.
  - let mut ptr = platform::alloc(key_len as usize + 1 + value_len as usize) as *mut c_char;
  + let mut ptr = platform::alloc(key_len as usize + 1 + value_len as usize + 1) as *mut c_char;
  copy_kv(ptr, key, value, key_len, value_len);
  put_new_env(ptr);
  }
  