Add flags for modern c++ to the target

CMakeLists.txt

@@ -8,7 +8,7 @@ include(CheckCXXCompilerFlag)
 enable_language(CXX)
 
 if(CMAKE_HOST_APPLE)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
+    list(APPEND CXX_EXTRA_FLAGS -stdlib=libc++)
 endif()
 
 set(ENABLE_CXXFLAGS_TO_CHECK 
@@ -24,7 +24,7 @@ foreach(flag ${ENABLE_CXXFLAGS_TO_CHECK})
     string(REPLACE "+" "x" flag_var ${flag_var})
     check_cxx_compiler_flag("${flag}" COMPILER_HAS_CXX_FLAG${flag_var})
     if(COMPILER_HAS_CXX_FLAG${flag_var})
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}")
+        list(APPEND CXX_EXTRA_FLAGS ${flag})
         break()
     endif()
 endforeach()
@@ -38,6 +38,7 @@ macro(add_test_executable TEST_NAME_)
     else()
         set(TEST_NAME "${TEST_NAME_}")
         add_executable (${TEST_NAME} EXCLUDE_FROM_ALL test/${TEST_NAME}.cpp)
+        target_compile_options(${TEST_NAME} PUBLIC ${CXX_EXTRA_FLAGS})
     endif()
     if(WIN32)
         add_test(NAME ${TEST_NAME} WORKING_DIRECTORY ${LIBRARY_OUTPUT_PATH} COMMAND ${TEST_NAME})
@@ -53,6 +54,7 @@ endmacro(add_test_executable)
 if (BIICODE) 
     INIT_BIICODE_BLOCK()
     ADD_BIICODE_TARGETS()
+    target_compile_options(${BII_LIB_TARGET} INTERFACE ${CXX_EXTRA_FLAGS})
     foreach (test ${BII_BLOCK_EXES})
         add_test_executable(${test})
     endforeach()