jeston xavier,the opencv issue of the sdk compatibility?

I just falsh the xavise os and all the sdk,which include opencv3.3.1,and i launch the command‘pkg-config opencv --modversion’,it’s working,opencv3.3.1 appeared.
Then i fellow the tutorial “”to install xavier,all is done.When i compile a library,it reminder me that i don’ have a “cv bridge”,and a strange thing is when i launch the command “pkg-config opencv --modversion”,it’s not working.???
Is that mean i must use the opencv in the sdk? or i can install another version opencv in my xavier?
Meantime i install the ros-melodic fellow the tutorial in the ros.wike,but it reminder me some dependency which exist,the ros-melodic can’t installed。
I am confused