Introduce a new CI test to validate out-of-tree builds
and prevent regressions in the `make export` workflow.
Specifically, this change adds `test-oot-build.sh` that:
* Builds NuttX using a selected configuration.
* Runs `make export` to generate the export package.
* Copies the `nuttx-export` to the OOT build project.
* Verifies that compilation and linking succeed.
Signed-off-by: trns1997 <trns1997@gmail.com>
d7b2df6d85