Ubuntu 18.04 + CUDA, backported GCC 5

configure \
    --enable-gpl\
    --enable-nonfree \
    --enable-shared \
    --enable-avresample \
    --enable-frei0r \
    --enable-gcrypt \
    --enable-gmp \
    --enable-gnutls \
    --enable-ladspa \
    --enable-libass \
    --enable-libcaca \
    --enable-libdc1394 \
    --enable-libfdk-aac \
    --enable-libflite \
    --enable-libfontconfig \
    --enable-libfreetype \
    --enable-libfribidi \
    --enable-libgsm \
    --enable-libmp3lame \
    --enable-libopus \
    --enable-libpulse \
    --enable-librsvg \
    --enable-librubberband \
    --enable-librtmp \
    --enable-libsmbclient \
    --enable-libsoxr \
    --enable-libspeex \
    --enable-libssh \
    --enable-libtheora \
    --enable-libtwolame \
    --enable-libvorbis \
    --enable-libvpx \
    --enable-libwavpack \
    --enable-libwebp \
    --enable-libx264 \
    --enable-libx265 \
    --enable-opengl \
    --enable-libdrm \
    --enable-vdpau \
    --cc=gcc-5 \
    --cxx=g++-5 \
    --enable-version3 \
    --enable-libspeex \
    --enable-libxvid \
    --enable-libvpx 
    --enable-nvenc \
    --enable-cuvid \
    --enable-cuda-nvcc \
    --nvcc="nvcc -ccbin /usr/bin/gcc-5"