CI pipeline for installer

[jkoritzinsky]

These were the changes I needed to get the CI pipeline building for the installer partition of the repository.

• update install-nuget-credprovider-then-build.sh to understand subsets (not strictly necessary, but it made things a bit cleaner in the initial prototyping day).
• Fix paths to the various YAML files included by the pipeline.
• Update the path mounted in the docker container to be root/runtime instead of root/coresetup.
• Fix paths for the manpages for the packaging steps.
• Disable signing during the installer build.
• Fix path to the cross directory
• Fix placeholder detection in tools-local to work correctly within the docker container.
• Fix parameters to installer.cmd and installer.sh to correctly pass --build and --restore on all platforms to restore the tools needed.