emulators/virtualbox-ose-71: Fix build on 15-CURRENT after 1500013

kBuild: Linking VBoxSVC
(...cut...) undefined reference to `cam_close_device'
(...cut...) undefined reference to `cam_freeccb'
(...cut...) undefined reference to `cam_getccb'
(...cut...) undefined reference to `cam_open_btl'
(...cut...) undefined reference to `cam_send_ccb'
(...cut...) undefined reference to `cam_strvis'
(...cut...) undefined reference to `geom_deletetree'
(...cut...) undefined reference to `geom_gettree'

PR: 286799
MFH: 2025Q2