Clean up make targets list-arch and list-toolchain to be much faster and
work without needing to invoke the archtecture's arch rules.mk. This
should make it work on machines that do not have that particular
toolchain in the path.
This is setting up for using it in the github action script.
list-arch and list-toolchain will compute and print the architecture and
toolchain needed to build the project the build is set to.
Used by the CI builder to decide what toolchain to grab.
