.github: workflows: Workflow for build_helpers

PR #63195 has managed to change code under test without
triggering those tests.

This change should remedy that by creating a new workflow,
based on twister_tests.yaml, that runs tests in
scripts/tests/build_helpers if build_helpers are modified.

Such a workflow should be easily extendable if we ever have more
non-Twister things to test in scripts/pylib.

Signed-off-by: Lukasz Mrugala <lukaszx.mrugala@intel.com>
2 files changed