Fixed build warnings (#6664)

* Fixed build warnings

* Suppress warning

* Suppress warning for sure

util/hash/build.rs

@@ -21,6 +21,6 @@
 extern crate gcc;
 
 fn main() {
-    gcc::compile_library("libtinykeccak.a", &["src/tinykeccak.c"]);
+    gcc::Build::new().file("src/tinykeccak.c").compile("libtinykeccak.a");
 }