using pathlib.py

def setup():
    import os, bpy, pathlib
   
    path = os.path.dirname(bpy.data.filepath)
    root = pathlib.Path(bpy.app.binary_path).parent
    
    # old way
    py = os.path.join(root, "2.80", "python", "include")
    build = os.path.join(path, "build")
    srcs = os.path.join(path, "voro", "src")
    
    print(f'{path}\n{root}\n{py}\n{build}\n{srcs}\n')
    
    # using pathlib.Path
    from pathlib import Path

    path = Path(bpy.data.filepath).parent
    root = Path(bpy.app.binary_path).parent
    
    py = Path(root) / "2.80" / "python" / "include"
    build = Path(path) / "build"
    srcs = Path(path) / "voro" / "src"
    print(f'{path}\n{root}\n{py}\n{build}\n{srcs}\n')    

setup()