Fix gdbstub not activating until the console is reset (#2245)

The check for initialising the gdbstub depending on whether the JIT was
enabled or not was the wrong way around: previously, it would only
enable the gdbstub if the JIT was enabled.

The stub started working again if you reset the console, as
NDS::SetGdbArgs didn't have any such check and it was called by
EmuInstance::updateConsole.

src/ARM.cpp

@@ -115,7 +115,7 @@ ARM::ARM(u32 num, bool jit, std::optional<GDBArgs> gdb, melonDS::NDS& nds) :
     Num(num), // well uh
     NDS(nds)
 {
-    SetGdbArgs(jit ? gdb : std::nullopt);
+    SetGdbArgs(jit ? std::nullopt : gdb);
 }
 
 ARM::~ARM()