Grab proot from bootstrap zip rather than including its nix path directly.

This means that the cachix substituter (or already having the package in your nix store somehow) is no longer required to build.

This required reworking the deploy script. As a bonus you can now omit the second argument and it will tell you what it would have copied instead of copying anything.

This is fixes one source of impurity, but for now flake builds will still require the --impure flag

scripts/setup.py

@@ -0,0 +1,13 @@
+from setuptools import setup, find_packages
+
+setup(
+    name='nix-on-droid-deploy-script',
+    version='0.0',
+    packages=[],
+    py_modules=["deploy"],
+    entry_points={
+        'console_scripts': [
+            'deploy=deploy:go',
+        ],
+    },
+)