Fix link error when building on docker.

.travis.yml

@@ -1,13 +1,12 @@
 language: rust
 
 rust:
-    - nightly
+    - nightly-2018-04-01
 
 cache: 
   cargo: true
 
 before_script:
-  - rustup override set nightly-2018-04-01
   - rustup component add rust-src
   - (test -x $HOME/.cargo/bin/cargo-install-update || cargo install cargo-update)
   - (test -x $HOME/.cargo/bin/xargo || cargo install xargo)

build.rs

@@ -4,5 +4,6 @@ fn main() {
     cc::Build::new()
 		.file("src/arch/x86_64/driver/apic/lapic.c")
 		.file("src/arch/x86_64/driver/keyboard/keyboard.c")
+		.flag("-mcmodel=large")
 		.compile("cobj");
 }