Fix emulator build (at least for devofs) using USE_NATIVE_FS=1 (#725)

* Fix emulator build (at least for devofs) using USE_NATIVE_FS=1

Author: PhracturedBlue

src/std.h

@@ -14,10 +14,14 @@
     #endif
 #else
     #ifndef USE_OWN_STDIO
-        #define USE_OWN_STDIO 0
-        #define fopen2(fat, p, m) fopen(p, m)
-        #define finit if(0) FS_Mount
-        void fempty(FILE *fh);
+        #if EMULATOR == USE_NATIVE_FS
+            #define USE_OWN_STDIO 0
+            #define fopen2(fat, p, m) fopen(p, m)
+            #define finit if (0) FS_Mount
+            void fempty(FILE *fh);
+        #else
+            #define USE_OWN_STDIO 1
+        #endif
     #endif
 #endif //EMULATOR