Fix a compilation warning with zephyr due to unused consts (may be used at application level)

Author: tomtom5152

src/unix/newlib/zephyr/mod.rs

@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 pub type c_char = i8;
 pub type c_long = i32;
 pub type c_ulong = u32;