fix(simulation): fix macOS gz SITL build

Add the GStreamer pkg-config library directories so the Gazebo camera plugin links cleanly with Homebrew installs on macOS. Cast ESC actuator outputs to double before publishing rotor velocities to avoid clang's -Wdouble-promotion build failure.

Signed-off-by: Dima Timofeev <dimkat@gmail.com>

src/modules/simulation/gz_bridge/GZMixingInterfaceESC.cpp

@@ -80,7 +80,7 @@ bool GZMixingInterfaceESC::updateOutputs(float outputs[MAX_ACTUATORS], unsigned
 		rotor_velocity_message.mutable_velocity()->Resize(active_output_count, 0);
 
 		for (unsigned i = 0; i < active_output_count; i++) {
-			rotor_velocity_message.set_velocity(i, outputs[i]);
+			rotor_velocity_message.set_velocity(i, static_cast<double>(outputs[i]));
 		}
 
 		if (_actuators_pub.Valid()) {

src/modules/simulation/gz_plugins/gstreamer/CMakeLists.txt

@@ -45,6 +45,11 @@ else()
         GstCameraSystem.cpp
     )
 
+    target_link_directories(${PROJECT_NAME}
+        PUBLIC ${GSTREAMER_LIBRARY_DIRS}
+        PUBLIC ${GSTREAMER_APP_LIBRARY_DIRS}
+    )
+
     target_link_libraries(${PROJECT_NAME}
         PUBLIC px4_gz_msgs
         PUBLIC ${GZ_SENSORS_TARGET}