libstrat: enable -Wextra, -Werror

This caught an embarrassingly large number of bugs.

libraries/libstratosphere/source/i2c/i2c_client_api.cpp

@@ -59,7 +59,7 @@ namespace ams::i2c {
 
         {
             std::scoped_lock lk(g_i2c_pcv_mutex);
-            g_i2c_pcv_manager = std::move(sp);
+            g_i2c_pcv_manager = std::move(sp_pcv);
             AMS_ABORT_UNLESS(g_i2c_pcv_count == 0);
             g_i2c_pcv_count = 1;
         }