fixed linker

Makefile

@@ -15,4 +15,4 @@ libovr-rs-44316370-0.1.so: libovr_wrapper.a lib.rs
 	rustc lib.rs -L .
 
 test: test.rs libovr-rs-44316370-0.1.so
-	rustc test.rs -L . --link-args="-lovr -ludev -lstdc++ -lc -lX11 -lm -lpthread -lXinerama"
+	rustc test.rs -L .

lib.rs

@@ -11,9 +11,11 @@ use cgmath::quaternion::Quat;
 use cgmath::vector::Vec3;
 use cgmath::matrix::Mat4;
 
+#[cfg(target_os = "linux")]
+#[link(name="udev")]
+#[link(name="stdc++")]
+#[link(name="Xinerama")]
 #[link(name="ovr_wrapper")]
-extern {}
-
 #[link(name="ovr")]
 extern {}