fix(ci): materialize rebar test src_dirs in shared test image. Refs EventHub/EventHubBack#36

docker/ci-test-prepare.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+# Replace rebar3 symlinks under _build/.../test with real copies (BusyBox cp -L fails on them).
+set -eu
+APP_ROOT="${APP_ROOT:-/app}"
+DEST="${APP_ROOT}/_build/test/lib/eventhub/test"
+mkdir -p "${DEST}"
+rm -rf "${DEST}/unit" "${DEST}/api"
+cp -a "${APP_ROOT}/test/unit" "${DEST}/unit"
+cp -a "${APP_ROOT}/test/api" "${DEST}/api"
+# shellcheck disable=SC2086
+cp -a ${APP_ROOT}/test/api_*_SUITE.erl "${DEST}/" 2>/dev/null || true
+
+if [ "$#" -gt 0 ]; then
+  exec "$@"
+fi