simulation: restore 'gazebo' alias for 'gazebo_iris'

- only create helper targets if Gazebo 11 found on system

boards/px4/sitl/default.px4board

@@ -44,7 +44,7 @@ CONFIG_MODULES_REPLAY=y
 CONFIG_MODULES_ROVER_POS_CONTROL=y
 CONFIG_MODULES_SENSORS=y
 CONFIG_COMMON_SIMULATION=y
-CONFIG_MODULES_SIMULATION_GZ_BRIDGE=y
+CONFIG_MODULES_SIMULATION_GZ_BRIDGE=n
 CONFIG_MODULES_TEMPERATURE_COMPENSATION=y
 CONFIG_MODULES_UUV_ATT_CONTROL=y
 CONFIG_MODULES_UUV_POS_CONTROL=y

src/modules/simulation/simulator_mavlink/sitl_targets_gazebo.cmake

@@ -1,3 +1,10 @@
+
+find_package(gazebo)
+
+if(gazebo_FOUND)
+
+	message(STATUS "Found gazebo-classic ${gazebo_VERSION}, including sitl_gazebo-classic simulator and targets")
+
 	# Estimate an appropriate number of parallel jobs
 	cmake_host_system_information(RESULT AVAILABLE_PHYSICAL_MEMORY QUERY AVAILABLE_PHYSICAL_MEMORY)
 	cmake_host_system_information(RESULT NUMBER_OF_LOGICAL_CORES QUERY NUMBER_OF_LOGICAL_CORES)
@@ -210,6 +217,8 @@ foreach(debugger ${debuggers})
 		endforeach()
 	endforeach()
 
+	add_custom_target(gazebo DEPENDS gazebo_iris) # alias
+
 	# mavsdk tests currently depend on sitl_gazebo
 	ExternalProject_Add(mavsdk_tests
 		SOURCE_DIR ${PX4_SOURCE_DIR}/test/mavsdk_tests
@@ -221,3 +230,4 @@ ExternalProject_Add(mavsdk_tests
 		EXCLUDE_FROM_ALL true
 		BUILD_ALWAYS 1
 	)
+endif()