Summary:
So far, the build process was configured for each job individually. This
was flexible in the past, when frequent changes were needed. Now, since
the CI build configurations are very stable, it is huge effort to keep
the jobs aligned during changes (e.g. Qt upgrade, build arguments etc).
This, plus the need to version control the build process has driven
the creation of this build script. The script is running on all nodes
and provides a small number of arguments to configure the build.
Python script for creating symbols is incorporated and therefore renamed.
Reviewers: #swift_pilot_client, msutcliffe
Subscribers: msutcliffe, jenkins
Differential Revision: https://dev.swift-project.org/D40
