"scripts": {
    "postpublish": [
        "mkdir /tmp/ffmpeg",
    ]
}

import zipfile
import os

srcFileName = os.getcwd() + '\bin\Release\netcoreapp1.0\prepublish.zip'
tmpFileName = os.getcwd() + '\bin\Release\netcoreapp1.0\publish.zip'

with zipfile.ZipFile(srcFileName, 'r') as sz:
    with zipfile.ZipFile(tmpFileName, 'w', zipfile.ZIP_DEFLATED) as z:
        for name in sz.namelist():
            srcFile = sz.open(name, "r")
            print(name)
            zi = zipfile.ZipInfo(name)
            zi.create_system = 3
            zi.external_attr = (0o764 << 16)
            z.writestr(zi, sz.read(name))
        z.close()
        sz.close()