chore: ignore almost-empty directories in nargo_cli tests

tooling/nargo_cli/build.rs

@@ -86,15 +86,22 @@
     let test_case_dirs =
         fs::read_dir(test_data_dir).unwrap().flatten().filter(|c| c.path().is_dir());
 
-    test_case_dirs.into_iter().map(|dir| {
+    test_case_dirs.into_iter().filter_map(|dir| {
+        // When switching git branches we might end up with non-empty directories that have a `target`
+        // directory inside them but no `Nargo.toml`.
+        // These "tests" would always fail, but it's okay to ignore them so we do that here.
+        if !dir.path().join("Nargo.toml").exists() {
+            return None;
+        }
+
         let test_name =
             dir.file_name().into_string().expect("Directory can't be converted to string");
         if test_name.contains('-') {
             panic!(
                 "Invalid test directory: {test_name}. Cannot include `-`, please convert to `_`"
             );
         }
-        (test_name, dir.path())
+        Some((test_name, dir.path()))
     })
 }
 
@@ -176,9 +183,9 @@
     let test_cases = test_cases.join("\n");
 
     // We need to isolate test cases in the same group, otherwise they overwrite each other's artifacts.
     // On CI we use `cargo nextest`, which runs tests in different processes; for this we use a file lock.
     // Locally we might be using `cargo test`, which run tests in the same process; in this case the file lock
     // wouldn't work, becuase the process itself has the lock, and it looks like it can have N instances without
     // any problems; for this reason we also use a `Mutex`.
     let mutex_name = format! {"TEST_MUTEX_{}", test_name.to_uppercase()};
     write!(