Update Dockerfile.amd64

Author: djthorpe

etc/Dockerfile.amd64

@@ -7,7 +7,8 @@ ARG BASE_CUDA_RUN_CONTAINER=nvidia/cuda:${CUDA_VERSION}-runtime-ubuntu${UBUNTU_V
 # Setup build container
 FROM ${BASE_CUDA_DEV_CONTAINER} AS build
 ARG CUDA_DOCKER_ARCH=all
-RUN add-apt-repository -y ppa:ubuntuhandbook1/ffmpeg6 \
+RUN apt-get -y install software-properties-common \
+ && add-apt-repository -y ppa:ubuntuhandbook1/ffmpeg6 \
  && apt-get -y update \
  && apt-get -y install build-essential git libgomp1 curl pkg-config \
  && apt-get -y install libavcodec-dev libavdevice-dev libavfilter-dev libavutil-dev libswscale-dev libswresample-dev