Fix generic docker build.

Closes #1945. Thanks to Andreas Schildbach.

ChangeLog.txt

@@ -8,6 +8,7 @@ Apps:
 
 Build:
 - Fix `install` target when using WITH_CJSON=no. Closes #1938.
+- Fix `generic` docker build. Closes #1945.
 
 
 2.0.2 - 2020-12-10

docker/generic/Dockerfile

@@ -1,19 +1,20 @@
-FROM alpine:latest AS build
+FROM alpine:edge AS build
 
 # A released dist version, like "1.2.3"
 ARG VERSION
 RUN test -n "${VERSION}"
 
 RUN apk --no-cache add \
  build-base \
- openssl-dev \
  c-ares-dev \
+ ca-certificates \
+ cjson-dev \
  curl \
- util-linux-dev \
  libwebsockets-dev \
  libxslt \
+ openssl-dev \
  python2 \
- ca-certificates
+ util-linux-dev
 
 # This build procedure is based on:
 # https://github.com/alpinelinux/aports/blob/master/main/mosquitto/APKBUILD
@@ -48,6 +49,7 @@ LABEL maintainer="Jonathan Hanson <[email protected]>" \
 RUN apk --no-cache add \
  busybox \
  ca-certificates \
+ cjson \
  openssl \
  libuuid \
  libwebsockets \