Fix latomic linking on Mac

SPE-1079

src/libslic3r/CMakeLists.txt

@@ -265,8 +265,11 @@ target_link_libraries(libslic3r
     ${CMAKE_DL_LIBS}
     )
 
-if (NOT MSVC)
-    target_link_libraries(libslic3r atomic) # no cmake magic for this...
+include(CheckAtomic)
+
+check_working_cxx_atomics(HAS_ATOMIC)
+if (NOT HAS_ATOMIC)
+    target_link_libraries(libslic3r atomic) 
 endif()
 
 if (TARGET OpenVDB::openvdb)