Add missing build-aux files

And tweak the .gitignore to reduce the chance that similar files are missed in
the future.

build-aux/test-env.in

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+# Guix Data Service -- Information about Guix over time
+# Copyright © 2019 Christopher Baines <mail@cbaines.net>
+#
+# This program is free software: you can redistribute it and/or
+# modify it under the terms of the GNU Affero General Public License
+# as published by the Free Software Foundation, either version 3 of
+# the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public
+# License along with this program.  If not, see
+# <http://www.gnu.org/licenses/>.
+
+export GUIX_DATA_SERVICE_DATABASE_PARAMSTRING=${GUIX_DATA_SERVICE_DATABASE_PARAMSTRING:-'dbname=guix_data_service_test user=guix_data_service'}
+
+"@abs_top_builddir@/pre-inst-env" "$@"
+exit $?