libmango: add temporary formatted log function

libmango/include-user/mango/log.h

@@ -3,8 +3,17 @@
 
 #include <mango/status.h>
 
+#undef TRACE
+
 extern kern_status_t kern_log(const char *s);
 
+#define kern_logf(...)                                                         \
+	do {                                                                   \
+		char s[128];                                                   \
+		snprintf(s, sizeof s, __VA_ARGS__);                            \
+		kern_log(s);                                                   \
+	} while (0)
+
 #ifdef TRACE
 #define kern_trace(...) kern_log(__VA_ARGS__)
 #define kern_tracef(...)                                                       \