How to pass parameter flags to gtest

I need help setting up gtest to add additional flags when compiling. Currently, I am getting this warning: warning: range-based ‘for’ loops only available with -std=c++11 or -std=gnu++11

My CMakeLists file looks like this:

cmake_minimum_required(VERSION 2.6)

find_package(GTest REQUIRED)

include_directories(${GTEST_INCLUDE_DIRS})

add_executable(runTests tests.cpp)

target_link_libraries(runTests ${GTEST_LIBRARIES} pthread)

It was created using this tutorial: http://ift.tt/2yKi2Ph

Where should I add the -std=c++11 flag to satisfy this warning?