This is necessary so source upgrades use the correct binary.
MFC after: 3 days
For the record: Problem spotted by Scott Long, who mentioned
that source upgrades from 4.7 to recent 5.x and 6.0 are broken.
Detailed analysis shows that 4.7 has a broken make(1) binary.
A breakage was fixed in RELENG_4 in make/main.c,v 1.35.2.7 by
imp@, though the commit log erroneously stated "MFC 1.68"
while in fact it should have been spelled as "MFC 1.67".