Fix and enable libnx compilation

[phcoder]

Tested on switch that it goes to menu and prompt

[schellingb]

Can you try running DOOM or another game made past 1993 on the default settings?
Because this would activate the dynamic recompiling CPU core which last time we tried Switch makes it crash. Without dynrec/jit this core isn't worth much IMHO. For similar reasons the WiiU port was abandoned, no one around capable of fixing it on those platforms. Dynrec/jit works perfectly fine for arm64 on phones and arm32 on phones and Pi, so it must just be some part of the special memory handling code that exists for Switch but there must be a mistake in there.

[schellingb]

Someone said the recent build made for Switch are (still) crashing when a game is started. I'm pretty sure that is the dynamic recompiling CPU (dynrec/jit) still not working properly. Not really sure what to do besides disabling Switch builds again... Would be nice to know if any of the other DOSBox cores work on Switch. Though a core could be working but dynrec might just be disabled for the Switch platform.