anchor.diff: -FROM alpine:3.6 as ffmpeg-builder
  +FROM alpine:3.7 AS ffmpeg-builder
   
   RUN apk add --no-cache \
     coreutils \
  
positive.code:   openssl-dev \
    lame-dev \
    libogg-dev \
    libvpx-dev \
    x265-dev
  
  # some -dev alpine packages lack .a files in 3.6 (some fixed in edge)
  RUN \
  
negative.code:   --enable-static \
    --pkg-config-flags=--static \
    --extra-ldflags=-static \
    --enable-gpl \
    --enable-nonfree \
    --enable-openssl \
  