ci: add plain build

Author: patricklodder

.cirrus.yml

@@ -163,3 +163,12 @@ task:
 #  env:
 #    << : *CIRRUS_EPHEMERAL_WORKER_TEMPLATE_ENV
 #    FILE_ENV: "./ci/test/00_setup_env_native_nowallet.sh"
+
+task:
+  name: '[depends] [focal]'
+  << : *GLOBAL_TASK_TEMPLATE
+  container:
+    image: ubuntu:focal
+  env:
+    << : *CIRRUS_EPHEMERAL_WORKER_TEMPLATE_ENV
+    FILE_ENV: "./ci/test/00_setup_env_native_plain.sh"

ci/test/00_setup_env_native_plain.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2020 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+export LC_ALL=C.UTF-8
+
+export CONTAINER_NAME=ci_native_plain
+export DOCKER_NAME_TAG=ubuntu:20.04
+export GOAL="install"
+export BITCOIN_CONFIG="--disable-tests --disable-bench"  # Use clang to avoid OOM
+
+# disabled until unit & functional tests are fully ported
+export RUN_UNIT_TESTS=false
+export RUN_FUNCTIONAL_TESTS=false