Don't normalize commands

Since commands are looked up in PATH, their `Path` is unreliable and
cannot be treated as a normal directory.

- Add an integration test
- Cleanup afterwards

Author: jyn514

tests/buildtest/inside_docker.rs

@@ -13,10 +13,14 @@ static CONTAINER_PREFIX: &str = "/outside";
 #[cfg(unix)]
 fn test_hello_world() {
     // regression test for https://github.com/rust-lang/rustwide/issues/30
-    if !Path::new("docker").exists() {
+    let already_present = Path::new("docker").exists();
+    if !already_present {
         std::fs::create_dir("docker").unwrap();
     }
     execute("buildtest::test_hello_world").unwrap();
+    if !already_present {
+        std::fs::remove_dir("docker").unwrap();
+    }
 }
 
 fn execute(test: &str) -> Result<(), Error> {

tests/integration/build_dir.rs

@@ -0,0 +1,14 @@
+use failure::Error;
+
+const WORKSPACE_NAME: &str = "test-drop";
+
+#[test]
+fn test_build_dir_drop() -> Result<(), Error> {
+    let workspace = crate::utils::init_named_workspace(WORKSPACE_NAME)?;
+	let mut build_dir = workspace.build_dir("drop-dir");
+	build_dir.purge_on_drop(true);
+	let path = build_dir.build_dir();
+	drop(build_dir);
+	assert!(!path.exists());
+	Ok(())
+}