Tests: No GNU Extensions

Avoid passing `-std=c++11` and `-std=gnu++11` with this?

test/CMakeLists.txt

@@ -30,18 +30,20 @@ find_package(Catch2 2.4.0 CONFIG REQUIRED)
 message(STATUS "Catch2: Found version ${Catch2_VERSION}")
 
 add_library(CatchMain CatchMain.cpp)
-# CMake 3.8.0+ feature:
+# CMake 3.8.0+ feature: use at least C++11
 # target_compile_features(CatchMain PUBLIC cxx_std_11)
 set_target_properties(CatchMain PROPERTIES
-#    CXX_EXTENSIONS OFF
-#    CXX_STANDARD_REQUIRED ON
+    #CXX_STANDARD 11  # use exactly C++11
+    #CXX_EXTENSIONS OFF
+    #CXX_STANDARD_REQUIRED ON
     POSITION_INDEPENDENT_CODE ON
     WINDOWS_EXPORT_ALL_SYMBOLS ON
 )
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
     target_compile_options(CatchMain PUBLIC "/bigobj")
 endif()
-target_link_libraries(CatchMain PUBLIC Catch2::Catch2)
+target_include_directories(CatchMain SYSTEM PUBLIC
+     ${Catch2_INCLUDE_DIRS})
 
 # NVCC does not incorporate the COMPILE_OPTIONS of a target but only the CMAKE_CXX_FLAGS
 IF(ALPAKA_ACC_GPU_CUDA_ENABLE AND NOT ALPAKA_CUDA_COMPILER MATCHES "clang")