Take core as a dependency on librlibc. This is needed so that it can

see the lang-items for Sized etc. @acrichto and @thestinger had no
objections.

mk/crates.mk

@@ -59,7 +59,7 @@ CRATES := $(TARGET_CRATES) $(HOST_CRATES)
 TOOLS := compiletest rustdoc rustc
 
 DEPS_core :=
-DEPS_rlibc :=
+DEPS_rlibc := core
 DEPS_unicode := core
 DEPS_alloc := core libc native:jemalloc
 DEPS_debug := std

src/librlibc/lib.rs

@@ -35,12 +35,13 @@
 // LLVM to optimize these function calls to themselves!
 #![no_builtins]
 
+#[phase(plugin, link)] extern crate core;
+
 #[cfg(test)] extern crate native;
 #[cfg(test)] extern crate test;
 #[cfg(test)] extern crate debug;
 
 #[cfg(test)] #[phase(plugin, link)] extern crate std;
-#[cfg(test)] #[phase(plugin, link)] extern crate core;
 
 // Require the offset intrinsics for LLVM to properly optimize the
 // implementations below. If pointer arithmetic is done through integers the