extrapatch-Config.kmk was merged in ports r528258 into the standard
Config.kmk patch out of necessity, but inadvertently missed that it was also
referenced in two other spots.
No PORTREVISION bump, as these are build-only fixes to fix the entirety of
virtualbox-ose-additions and the DEBUG option of virtualbox-ose-kmod.
PR: 245239
Approved by: koobs (mentor)
Approved by: portmgr (blanket: build fix, just-fix-it)
MFH: 2020Q2 (blanket: build fix)
Differential Revision: https://reviews.freebsd.org/D24260
e4f412cb1b