preserve metadata when copying APK signatures

preserve metadata when copying APK signatures

Since this code was not setting the "create system" and "compress type",
Python uses it's defaults.  Those will be different than what the Android
tools produces if this is run on UNIX.  The Android tools uses the bare
bones "Windows" ZIP format, e.g. no permissions, etc.

For example:
https://verification.f-droid.org/eu.siacs.conversations_234.apk.diffoscope.html