Support proper locating of Nest.toml; Cleanup.

src/env.rs

@@ -35,10 +35,7 @@ pub fn get_javac_ver() -> anyhow::Result<semver::Version> {
 }
 
 pub fn set_cwd<P: AsRef<Path>>(path: P) -> io::Result<()> {
-    let mut cwd = crate::PROJECT_ROOT
-        .lock()
-        .expect("Failed to lock Mutex")
-        .to_owned();
+    let mut cwd = crate::PROJECT_ROOT.clone();
     cwd.push(path.as_ref());
-    std::env::set_current_dir(cwd)
+    std::env::set_current_dir(cwd.as_path())
 }