Switch atmosphere's build target to C++20. (#952)

* ams: update to build with gcc10/c++20

* remove mno-outline-atomics

* ams: take care of most TODO C++20s

* fusee/sept: update for gcc10

* whoosh, your code now uses pre-compiled headers

* make: dependency fixes

libraries/libstratosphere/include/stratosphere/fssystem/buffers/fssystem_file_system_buddy_heap.hpp

@@ -30,7 +30,7 @@ namespace ams::fssystem {
             class PageList;
 
             struct PageEntry { PageEntry *next; };
-            static_assert(std::is_pod<PageEntry>::value);
+            static_assert(util::is_pod<PageEntry>::value);
             static_assert(sizeof(PageEntry) <= BlockSizeMin);
 
             class PageList : public ::ams::fs::impl::Newable {