message: add libpng to builder
diff: @@ -25,6 +25,7 @@ RUN apk update \
  bash \
  ca-certificates \
  wget \
  + libpng-dev \
  && wget -q -O /etc/apk/keys/sgerrand.rsa.pub https://raw.githubusercontent.com/sgerrand/alpine-pkg-glibc/master/sgerrand.rsa.pub \
  && wget https://github.com/sgerrand/alpine-pkg-glibc/releases/download/2.26-r0/glibc-2.26-r0.apk \
  && apk add glibc-2.26-r0.apk \
  