fix Docker build (smicallef#1145)

Dockerfile

@@ -30,11 +30,11 @@
 #   sudo docker build -t spiderfoot-test --build-arg REQUIREMENTS=requirements_test.txt .
 #   sudo docker run --rm spiderfoot-test -m pytest --flake8 .
 
-FROM alpine:3.9.6 AS build
+FROM alpine:3.12.4 AS build
 ARG REQUIREMENTS=requirements.txt
 RUN apk add --no-cache gcc git curl python3 python3-dev py3-pip swig tinyxml-dev \
  python3-dev musl-dev openssl-dev libffi-dev libxslt-dev libxml2-dev jpeg-dev \
- openjpeg-dev zlib-dev
+ openjpeg-dev zlib-dev cargo rust
 RUN python3 -m venv /opt/venv
 ENV PATH="/opt/venv/bin":$PATH
 COPY $REQUIREMENTS requirements.txt ./
@@ -44,7 +44,7 @@ RUN pip3 install -r "$REQUIREMENTS"
 
 
 
-FROM alpine:3.9.6
+FROM alpine:3.12.4
 WORKDIR /home/spiderfoot
 # Place database and configs outside installation directory
 ENV SPIDERFOOT_DATA /var/lib/spiderfoot