initial support for Google Cloud builds

[adrianschroeter]

Not yet ready to merge:

• detect disk device on attach and adapt CLI for it
• fix hardcoded names (vm-2 and friends)
• cleanup

issues to fix for becoming productive

• look into a way how to use disk encryption
• look into a way to setup bootloader without possible conflicts in build environment
• fix random build failures
• improve serial log behaviour
• looking for speedups .... we need currently 3 minutes on new hardware of gcloud versus 20 seconds on old hardware with kvm
• add support to inject sysrq events ... how?
• find a way to avoid the need of a 10GB storage device even for the smallest build

[adrianschroeter]

Not yet ready to merge ... the pull request is just for discussion

[michaeldtz]

description of topic: look into a way to setup bootloader without possible conflicts in build environment --> kernel needs to be in the build image. In current use cases the kernel is provisioned from outside.