clang: warning: -lgtest: 'linker' input unused - c++

Question

I'm developing applications in C++11 and my compiler is CLang++ 3.3. I'm also using Netbeans 7.3 IDE on Linux Mint 14.
All of my tests are done with GoogleTest (gtest-1.6.0) and almost everything is working fine except the warning mentioned in the title of this post.
Here's the command line executed by netbeans as an example:
clang++ -pedantic-errors -lgtest -pthread -c -g -Wall -std=c++11 -pedantic-errors -lgtest -pthread -MMD -MP -MF build/Debug/CLang-Linux-x86/_ext/1802678175/main.o.d -o build/Debug/CLang-Linux-x86/_ext/1802678175/main.o ../GIT_CryptoCode/src/main.cpp
I don't know why, but the command contains twice some attributes which gives the same warning twice of course. This is what I did in the project properties :
If I remove the Additional options, gtest is not working and the command line becomes something like this : clang++ -c -g -Wall -std=c++11 .... What should I do to not get some attributes to be duplicates ?
Well, even with cmake, I got the warning with Clang (which appears once this time :)). I also tested with GCC 4.7 and I didn't get any warning. Here's the command line I use in a cmake file for GCC :
set (CMAKE_CXX_FLAGS "-Winline -Wall -Werror -pedantic-errors -pthread -std=c++11")
Thus, Clang seems to be the problem. Is anyone know where this warning come from and how to remove it ? Is this a Clang bug ?
Thanks for your help.

Answer 1

I want to thank #Fraser for his help that helps me to find out the way to remove the warnings. Basically, instead of writing -pedantic-errors -lgtest -pthread in the Additional options of the C++ compiler section which gives a duplicate warning, these attributes should be in the Linker section of the project.
So, the Additional Options in the C++ compiler section are left empty. Now, I can use the -Werror attribute without any problem.
Also, in the cmake file, the line
target_link_libraries(${Project_Name} ${GTEST_BOTH_LIBRARIES})
links the gtest library to the project. Thus, no need of -lgtest in
set (CMAKE_CXX_FLAGS "-Winline -Wall -Werror -pedantic-errors -pthread -std=c++11")
both, for GCC and Clang.