Add installer build/test to the runtime.yml pipeline (#705)

Add installer build/test to the runtime.yml pipeline (#705)

* First pass to get an installer build integrated into runtime.yml with minimal changes to the installer jobs.

Fix paths to jobs.

Fix typos

Add platform to parameter lists.

Pass platform to all jobs.

Cleanup variable usages.

Don't pass buildConfig down to installer jobs. They use matrix strategy instead.

Fix variable usage in windows build.

Fix windows platform names.

Add missing platform parameter for Windows_NT_arm

Update last condition re parameters.dockerImage.

Rename dockerImage parameter to productBuildDockerImage to be more explicit.

Use pool and container parameters from platform-matrix in installer build.

Pass rootfs dir via crossrootfsDir to bash-build.yml.

Fix passing down container in runtime-installer pipeline.

Remove unused Linux_x64_raw config.

* Add support for clang 9 to corehost build.

* Skip tests on Linux_musl_arm64

* runtime.yml installer build with live artifacts

Includes refactoring the runtime legs to avoid duplicating artifact
transfer logic and preserve the runtime standalone build.

* Fix installer overrides: accept live CI artifacts

* Use clone-checkout-bundle-step.yml everywhere

* Try using isOfficialBuild var from template expr

* Switch from $[] to $() to fix clone template

$[] becomes empty string when a variable is undefined. $() sticks around literally if the variable doesn't exist, messing up the command. Unfortunately $[] doesn't seem to work in this context so we must use $() and define the variable as empty string.