qemu_multiarch_testing: update

* qemu_multiarch_testing/.gitignore: New file.
* qemu_multiarch_testing/README: Update statistics.
* qemu_multiarch_testing/hdc.dir/init2: Run "make check".
* qemu_multiarch_testing/make-hdc-img.sh: Robustify,
automatically calculate hdc image size.
* qemu_multiarch_testing/parallel-build-hdc-img.sh: Reduce
hdb image size.  Report completion of each parallelized task.
5 files changed