install extra dependencies

Dockerfile

@@ -9,18 +9,16 @@ ENV SUTTY=sutty.nl
 ENV HTTP_BASIC_USER=sutty
 ENV HTTP_BASIC_PASSWORD=gibberish
 ENV NOKOGIRI_USE_SYSTEM_LIBRARIES=1
+ENV EXTRA_PKGS=''
 
 RUN gem install --no-user-install --no-document --source https://rubygems.org geminabox mini_portile2 gem-compiler
 
 COPY ./gemcompiler.sh /usr/local/bin/gemcompiler
-RUN chmod 755 /usr/local/bin/gemcompiler
+COPY ./bootstrap.sh /usr/local/bin/bootstrap
 
 RUN install -dm 2750 -o builder -g builder /srv/gems
 VOLUME /srv/gems
 
-RUN apk add --no-cache file-dev
-RUN apk add --no-cache libssh2-dev
-RUN apk add --no-cache libc6-compat libstdc++
+RUN apk add --no-cache su-exec file-dev libssh2-dev libc6-compat libstdc++
 
-USER builder
-ENTRYPOINT /usr/local/bin/gemcompiler
+ENTRYPOINT /usr/local/bin/bootstrap

bootstrap.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+set -e
+set -x
+
+test -n "${EXTRA_PKGS}" && apk add --no-cache ${EXTRA_PKGS}
+
+su-exec builder /usr/local/bin/gemcompiler