Fix some more GCC warnings, mark some bugs based on GCC warnings (#2309)

* Fix some more GCC warnings, mark some bugs based on GCC warnings

* Weird formatting

* Suggested changes

* More weird indentation I guess

* UNREACHABLE() macro, add missing NORETURNs to fault_n64.c

* AVOID_UB for PAL path in z_file_nameset.c

* Remove comments about return types

* Remove temp no longer needed

include/attributes.h

@@ -1,6 +1,8 @@
 #ifndef ATTRIBUTES_H
 #define ATTRIBUTES_H
 
+#include "versions.h"
+
 #if !defined(__GNUC__) && !defined(__attribute__)
 #define __attribute__(x)
 #endif
@@ -11,4 +13,17 @@
 #define NO_REORDER   __attribute__((no_reorder))
 #define SECTION_DATA __attribute__((section(".data")))
 
+#ifdef __GNUC__
+#define UNREACHABLE() __builtin_unreachable()
+#else
+#define UNREACHABLE()
+#endif
+
+// Variables may be unused in retail versions but used in debug versions
+#if DEBUG_FEATURES
+#define UNUSED_NDEBUG
+#else
+#define UNUSED_NDEBUG UNUSED
+#endif
+
 #endif