Add cfail test for late resources

tests/cfail/late-resource-init.rs

+#![deny(warnings)]
+#![feature(proc_macro)]
+#![no_std]
+
+extern crate cortex_m_rtfm as rtfm;
+extern crate stm32f103xx;
+
+use rtfm::{app, Threshold};
+
+app! {
+    device: stm32f103xx,
+
+    resources: {
+        static A: u8 = 0;
+        static LATE: u8;
+    },
+
+    tasks: {
+        EXTI0: {
+            path: exti0,
+            priority: 1,
+            resources: [A, LATE],
+        },
+
+        EXTI1: {
+            path: exti1,
+            priority: 2,
+            resources: [A, LATE],
+        },
+    },
+}
+
+fn init(_p: init::Peripherals, r: init::Resources) -> init::LateResourceValues {
+    // Try to use a resource that's not yet initialized:
+    r.LATE;
+    //~^ error: no field `LATE`
+
+    init::LateResourceValues {
+        LATE: 0,
+    }
+}
+
+fn idle() -> ! {
+    loop {}
+}
+
+fn exti0(_t: &mut Threshold, _r: EXTI0::Resources) {}
+
+fn exti1(_t: &mut Threshold, _r: EXTI1::Resources) {}