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/source/ams/ams_environment.cpp

@@ -13,7 +13,6 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-
 #include <stratosphere.hpp>
 #include "ams_bpc.h"
 
@@ -182,6 +181,9 @@ extern "C" {
 
 /* Custom abort handler, so that std::abort will trigger these. */
 void abort() {
+    static ams::os::Mutex abort_lock(true);
+    std::scoped_lock lk(abort_lock);
+
     ams::AbortImpl();
     __builtin_unreachable();
 }