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/libvapours/include/vapours/includes.hpp

@@ -28,6 +28,7 @@
 
 /* C++ headers. */
 #include <type_traits>
+#include <concepts>
 #include <algorithm>
 #include <iterator>
 #include <limits>
@@ -38,6 +39,8 @@
 #include <functional>
 #include <tuple>
 #include <array>
+#include <bit>
+#include <span>
 
 /* Stratosphere wants additional libstdc++ headers, others do not. */
 #ifdef ATMOSPHERE_IS_STRATOSPHERE