Firstly, this is not an error. It is a warning. Therefore it wont stop your build. If your build is failing, it is because of something else.
What this warning means is that there are two or more libraries or programs in your build that require the same .o file. This isn't currently a problem but if you (say) change the compile switches for one instance, it'll mean you have 2 incompatible sets of requirements for the same object, and that will result in a build error.