MFC r318211:

Fix up previous commit

• Apply the logic to the FreeBSD block
• Fix a typo with the getconf(1) call that I would have caught, were it not for the fact that I got the blocks wrong.
• Consolidate the hardcoded buffer sizes to the NetBSD block.

This would have been discovered had I run the test on a system where
PATH_MAX != 1024 (I don't have that at my disposal right at this moment).

MFC with: r318210