cirrus: Add smoke testing for builtin plugins

This adds two example plugins within testing/builtin-plugins/Files:

* protocol-plugin copied over from testing/btest/plugins/protocol-plugin

* py-lib-plugin that embeds Python to have a dependency on an external
  shared library which was already available in CI and fun to use, too.

Closes #2837

testing/builtin-plugins/Files/py-lib-plugin/CMakeLists.txt

@@ -0,0 +1,34 @@
+cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
+
+find_package(PythonLibs REQUIRED)
+
+file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/VERSION" VERSION LIMIT_COUNT 1)
+
+string(REGEX REPLACE "[.-]" " " version_numbers ${VERSION})
+separate_arguments(version_numbers)
+list(GET version_numbers 0 VERSION_MAJOR)
+list(GET version_numbers 1 VERSION_MINOR)
+list(GET version_numbers 2 VERSION_PATCH)
+
+# Our plugin source and scripts are in a subdirectory
+set(BRO_PLUGIN_BASE "${CMAKE_CURRENT_SOURCE_DIR}/plugin")
+
+include(ZeekPlugin)
+
+include_directories(BEFORE ${PYTHON_INCLUDE_DIR})
+
+zeek_plugin_begin(Zeek PyLib)
+
+file(GLOB cc_files RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "plugin/src/*.cc")
+foreach(file ${cc_files})
+    zeek_plugin_cc(${file})
+endforeach ()
+
+file(GLOB bif_files RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "plugin/src/*.bif")
+foreach(file ${bif_files})
+    zeek_plugin_bif(${file})
+endforeach ()
+
+zeek_plugin_dist_files(README VERSION)
+zeek_plugin_link_library(${PYTHON_LIBRARY})
+zeek_plugin_end()

testing/builtin-plugins/Files/py-lib-plugin/README

@@ -0,0 +1,8 @@
+PyLib
+=====
+
+Embedding Python with a plugin.
+
+    zeek -e 'Python::run_simple_string("import this")'
+
+Mostly to test a link dependency of a builtin plugin.

testing/builtin-plugins/Files/py-lib-plugin/VERSION

@@ -0,0 +1 @@
+0.0.1

testing/builtin-plugins/Files/py-lib-plugin/plugin/src/Plugin.cc

@@ -0,0 +1,34 @@
+#include "Plugin.h"
+
+extern "C"
+	{
+#include <Python.h>
+	}
+
+namespace zeek::plugin::Zeek_PyLib
+	{
+Plugin plugin;
+	}
+
+using namespace zeek::plugin::Zeek_PyLib;
+
+zeek::plugin::Configuration Plugin::Configure()
+	{
+	zeek::plugin::Configuration config;
+	config.name = "Zeek::PyLib";
+	config.description = "Plugin embedding Python, whoosh.";
+	config.version.major = 0;
+	config.version.minor = 0;
+	config.version.patch = 1;
+	return config;
+	}
+
+void Plugin::InitPostScript()
+	{
+	Py_Initialize();
+	}
+
+void Plugin::Done()
+	{
+	Py_FinalizeEx();
+	}

testing/builtin-plugins/Files/py-lib-plugin/plugin/src/Plugin.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <zeek/plugin/Plugin.h>
+
+namespace zeek::plugin
+	{
+namespace Zeek_PyLib
+	{
+
+class Plugin : public zeek::plugin::Plugin
+	{
+protected:
+	zeek::plugin::Configuration Configure() override;
+	void InitPostScript() override;
+	void Done() override;
+	};
+
+extern Plugin plugin;
+
+	}
+	}

testing/builtin-plugins/Files/py-lib-plugin/plugin/src/pylib.bif

@@ -0,0 +1,18 @@
+module Python;
+
+%%{
+extern "C" {
+#include <Python.h>
+}
+%%}
+
+function version%(%): string
+%{
+	return zeek::make_intrusive<zeek::StringVal>(Py_GetVersion());
+%}
+
+function run_simple_string%(s: string%): bool
+%{
+	PyRun_SimpleString(s->CheckString());
+	return zeek::val_mgr->True();
+%}