add simple entrypoint script

docker-entrypoint.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+if [ "${GCE_SSH_KEY}" ]; then
+    echo "${GCE_SSH_KEY}" > $HOME/.ssh/google_compute_engine
+    chmod 600 $HOME/.ssh/google_compute_engine
+fi
+
+if [ "${GCE_CREDENTIALS_JSON}" ] && [ "${GCE_CREDENTIALS_FILE}" ]; then
+    DIR=$(dirname "${GCE_CREDENTIALS_FILE}")
+    mkdir -p "${DIR}"
+    echo "${GCE_CREDENTIALS_JSON}" > "${GCE_CREDENTIALS_FILE}"
+fi
+
+if [ "${MOLECULE_CUSTOM_MODULES_REPO}" ]; then
+    mkdir ./library/
+    git clone "${MOLECULE_CUSTOM_MODULES_REPO}" ./library/
+fi

docker/Dockerfile.gce

@@ -20,6 +20,8 @@ ENV PIP_PACKAGES="\
     pycrypto \
 "
 
+COPY ./docker-entrypoint.sh /
+
 RUN \
     apk update \
     && apk add --update --no-cache ${PACKAGES} \
@@ -32,3 +34,4 @@ RUN \
 
 USER root
 ENV SHELL /bin/bash
+ENTRYPOINT ["/docker-entrypoint.sh"]