Various fixes

* Retrieve build commands from build_manager
* fixing psa build dir
* Use different node labels for different builds
* Add script to download jenkins artifacts
* Verify status per stage
* Moving code to library
* Ability to comment on gerrit change

Change-Id: I390674b7ed6cfd20e4746a2d32e708fd6855857b
Signed-off-by: Dean Birch <dean.birch@arm.com>
12 files changed