Add rlibc dependency for memset, memcpy, etc.

Cargo.toml

@@ -5,3 +5,6 @@ authors = ["Philipp Oppermann <dev@phil-opp.com>"]
 
 [lib]
 crate-type = ["staticlib"]
+
+[dependencies]
+rlibc = "*"

src/lib.rs

@@ -15,6 +15,8 @@
 #![feature(no_std, lang_items)]
 #![no_std]
 
+extern crate rlibc;
+
 #[no_mangle]
 pub extern fn main() {
     // ATTENTION: we have a very small stack and no guard page