irods_plugin_dependencies needs to pass down ${CMAKE_DL_LIBS}

[SwooshyCueb]

irods_plugin_dependencies links privately to ${CMAKE_DL_LIBS}:

irods/lib/core/CMakeLists.txt

Lines 168 to 175 in e4b4e8a

	target_link_libraries(
	irods_plugin_dependencies
	PRIVATE
	"${IRODS_EXTERNALS_FULLPATH_BOOST}/lib/libboost_filesystem.so"
	"${IRODS_EXTERNALS_FULLPATH_BOOST}/lib/libboost_random.so"
	"${IRODS_EXTERNALS_FULLPATH_BOOST}/lib/libboost_system.so"
	${CMAKE_DL_LIBS}
	)

However, the public header irods_load_plugin.hpp references symbols from libdl in multiple locations:

irods/lib/core/include/irods/irods_load_plugin.hpp

Lines 464 to 502 in e4b4e8a

	// =-=-=-=-=-=-=-
	// try to open the shared object
	const auto rtld_flags = get_plugin_rtld_flags(so_name);
	void* handle = dlopen(so_name.c_str(), rtld_flags);
	if ( !handle ) {
	std::stringstream msg;
	msg << "failed to open shared object file [" << so_name
	<< "] :: dlerror: is [" << dlerror() << "]";
	return ERROR( PLUGIN_ERROR, msg.str() );
	}
	// =-=-=-=-=-=-=-
	// clear any existing dlerrors
	dlerror();
	// =-=-=-=-=-=-=-
	// attempt to load the plugin factory function from the shared object
	typedef PluginType* ( *factory_type )( const std::string& , const Ts&... );
	factory_type factory = reinterpret_cast< factory_type >( dlsym( handle, "plugin_factory" ) );
	char* err = dlerror();
	if ( 0 != err || !factory ) {
	std::stringstream msg;
	msg << "failed to load symbol from shared object handle - plugin_factory"
	<< " :: dlerror is [" << err << "]";
	dlclose( handle );
	return ERROR( PLUGIN_ERROR, msg.str() );
	}
	rodsLog(LOG_DEBUG, "load_plugin - calling plugin_factory() in [%s]", so_name.c_str());
	// =-=-=-=-=-=-=-
	// using the factory pointer create the plugin
	_plugin = factory( _instance_name, _args... );
	if ( !_plugin ) {
	std::stringstream msg;
	msg << "failed to create plugin object for [" << _plugin_name << "]";
	dlclose( handle );
	return ERROR( PLUGIN_ERROR, msg.str() );
	}

irods_plugin_dependencies must link ${CMAKE_DL_LIBS} publicly to pass down this dependency.
Better yet, the linkage should be moved to the irods_plugin_dependencies_obj target as well.