Add infrastructure for compiletests

Also adds compilefail tests for some lints, closes #5646.

tests/compiletest/helper/lib.rs

@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate compiletest_rs as compiletest;
+
+use std::env;
+use std::path::PathBuf;
+
+pub fn run_mode(mode: &'static str) {
+
+    let mut config = compiletest::default_config();
+    let cfg_mode = mode.parse().ok().expect("Invalid mode");
+
+    config.mode = cfg_mode;
+    config.src_base = PathBuf::from(format!("{}", mode));
+
+    let mut base_path = env::current_dir().expect("Current directory is invalid");
+    base_path.pop();
+    base_path.pop();
+    base_path.pop();
+
+    let mode = env::var("BUILD_MODE").expect("BUILD_MODE environment variable must be set");
+    let debug_path = base_path.join(PathBuf::from(format!("target/{}", mode)));
+    let deps_path = base_path.join(PathBuf::from(format!("target/{}/deps", mode)));
+
+    config.target_rustcflags = Some(format!("-L {} -L {}",  debug_path.display(), deps_path.display()));
+    compiletest::run_tests(&config);
+}