Compute src_dir from original filename

This fixed a bug where bindgen was providing cwd() for src_dir,
but actually the src_dir should have been based on the filename.
This prevents that problem from happening in the future!

crates/ast/src/module.rs

@@ -10,15 +10,6 @@ pub fn load_module(src_file: &Path, threading: Threading) -> LoadedModule {
     let loaded = roc_load::load_and_typecheck(
         &arena,
         src_file.to_path_buf(),
-        src_file
-            .parent()
-            .unwrap_or_else(|| {
-                panic!(
-                    "src_file {:?} did not have a parent directory but I need to have one.",
-                    src_file
-                )
-            })
-            .to_path_buf(),
         subs_by_module,
         TargetInfo::default_x86_64(),
         roc_reporting::report::RenderTarget::ColorTerminal,