[Libc][Minilibc] Add some function declaration to time.h .

components/libc/compilers/minilibc/time.h

@@ -3,4 +3,14 @@
 
 #include <sys/time.h>
 
+time_t mktime(struct tm * const t);
+
+char *asctime(const struct tm *timeptr);
+char *ctime(const time_t *timep);
+struct tm* localtime(const time_t* t);
+
+char *asctime_r(const struct tm *t, char *buf);
+struct tm *gmtime_r(const time_t *timep, struct tm *r);
+struct tm* localtime_r(const time_t* t, struct tm* r);
+
 #endif