Build - Store the base64 release key in the OTA zips

This can be directly grepped in pre-existing package.xml tables
to make sure we're not trying to update to a differently signed
build

Change-Id: I8073d35c43a9dc7eedb694e1df6a57751bc4a8d0
Signed-off-by: STELIX <ssspinni@gmail.com>
Build - use /usr/bin/env to call python

Hardcoding the path to python instead of env is not recommended.  This
can break the build in some Linux environments that link /usr/bin/python
to python3.

Change-Id: I561a2463077193e24dcf57a8134fa55700be86e5
Signed-off-by: STELIX <ssspinni@gmail.com>