kdrive: Explicitly ignore errors from the -switchCmd script

Make it clear that we intentionally ignore the -switchCmd return
value. This keeps GCC from emitting a warning when the server is
compiled with -D_FORTIFY_SOURCE=2.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Jamey Sharp <jamey@minilop.net>

hw/kdrive/src/kdrive.c

@@ -118,10 +118,17 @@ KdDoSwitchCmd(const char *reason)
 {
     if (kdSwitchCmd) {
         char *command;
+        int ret;
 
         if (asprintf(&command, "%s %s", kdSwitchCmd, reason) == -1)
             return;
-        system(command);
+
+        /* Ignore the return value from system; I'm not sure
+         * there's anything more useful to be done when
+         * it fails
+         */
+        ret = system(command);
+        (void) ret;
         free(command);
     }
 }