Function assemble_project_with_deps 

pub fn assemble_project_with_deps(
    entry_path: &Path,
    dep_roots: Vec<DepRoot>,
) -> Result<AssembledProgram, String>

assemble_project, additionally linking the declared dependency roots so a bare Import <Dep>. resolves against a path/git-local package outside the project root. dep_roots empty is byte-for-byte identical to assemble_project, so a single-project build is unchanged.