cmake: rename and move runner_yml_props_target to boilerplate

Rename it to "runners_yaml_props_target", because the file name is
runners.yaml, not runner.yml.

Move it to the boilerplate definition so that we can modify it before
cmake/flash/CMakeLists.txt gets run.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
2 files changed