build-gnu.sh: Build GNU arch and reduce build time

[oech3]

GNU test for arch command was disabled since GNU does not build it by default. But uutils builds arch by default. So we should enable it.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/chcon/chcon-fail is now being skipped but was previously passing.
Note: The gnu test tests/runcon/runcon-compute is now being skipped but was previously passing.

[oech3]

I think #9314 should be merged at same time.