deal with some gcc7+ warnings

pico/cd/cd_image.c

@@ -11,6 +11,10 @@
 #include "cdd.h"
 #include "cue.h"
 
+#if defined(__GNUC__) && __GNUC__ >= 7
+#pragma GCC diagnostic ignored "-Wformat-truncation"
+#endif
+
 static int handle_mp3(const char *fname, int index)
 {
   track_t *track = &cdd.toc.tracks[index];

platform/common/emu.c

@@ -28,6 +28,10 @@
 #include <pico/pico_int.h>
 #include <pico/patch.h>
 
+#if defined(__GNUC__) && __GNUC__ >= 7
+#pragma GCC diagnostic ignored "-Wformat-truncation"
+#endif
+
 #ifndef _WIN32
 #define PATH_SEP      "/"
 #define PATH_SEP_C    '/'