multimedia/webcamoid: unbreak after r490611

===> Installing existing package /packages/All/ffmpeg-4.1_4,1.txz
[112amd64-default-job-07] Installing ffmpeg-4.1_4,1...
[112amd64-default-job-07] `-- Installing libva-2.3.0_2...
-[112amd64-default-job-18] | `-- Installing v4l_compat-1.6.3_3...
-[112amd64-default-job-18] | `-- Extracting v4l_compat-1.6.3_3: .......... done

> Building package for webcamoid-8.1.0_9

pkg-static: Unable to access file /wrkdirs/usr/ports/multimedia/webcamoid/work/stage/usr/local/lib/avkys/submodules/VideoCapture/libv4l2sys.so:No such file or directory
pkg-static: Unable to access file /wrkdirs/usr/ports/multimedia/webcamoid/work/stage/usr/local/lib/avkys/submodules/VideoCapture/libv4lutils.so:No such file or directory
pkg-static: Unable to access file /wrkdirs/usr/ports/multimedia/webcamoid/work/stage/usr/local/lib/avkys/submodules/VirtualCamera/libv4l2sys.so:No such file or directory
pkg-static: Unable to access file /wrkdirs/usr/ports/multimedia/webcamoid/work/stage/usr/local/lib/avkys/submodules/VirtualCamera/libv4lutils.so:No such file or directory

Reported by: pkg-fallout