Removes CMake warning about missed rpath on MacOS for libgtest.so

ThirdParty/common/gtest/CMakeLists.txt

@@ -9,5 +9,11 @@ if(MSVC)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D_VARIADIC_MAX=10 /wd4100 /wd4275")
 endif()
 
+# instructs CMake to consider libgtest.so as our project library (inspite of the fact, that
+# it is not installed) and to provide @rpath instead of hardcoded links.
+if(APPLE)
+   set(CMAKE_MACOSX_RPATH 1)
+endif()
+
 option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)." ON)
 add_subdirectory(gtest-1.8.0)