[libc][timezone] implement lightweith timezone configuration

components/libc/compilers/common/include/sys/time.h

@@ -28,19 +28,8 @@ extern "C" {
 #define CLOCKS_PER_SEC RT_TICK_PER_SECOND
 
 /* timezone */
+/* this method of representing timezones has been abandoned */
 #define DST_NONE    0   /* not on dst */
-#define DST_USA     1   /* USA style dst */
-#define DST_AUST    2   /* Australian style dst */
-#define DST_WET     3   /* Western European dst */
-#define DST_MET     4   /* Middle European dst */
-#define DST_EET     5   /* Eastern European dst */
-#define DST_CAN     6   /* Canada */
-#define DST_GB      7   /* Great Britain and Eire */
-#define DST_RUM     8   /* Rumania */
-#define DST_TUR     9   /* Turkey */
-#define DST_AUSTALT 10  /* Australian style with shift in 1986 */
-
-struct itimerspec;
 
 struct timezone
 {
@@ -48,6 +37,15 @@ struct timezone
     int tz_dsttime;       /* type of dst correction */
 };
 
+/* lightweight timezone and daylight saving time */
+#ifdef RT_LIBC_USING_LIGHT_TZ_DST
+void rt_tz_set(int32_t offset_sec);
+int32_t rt_tz_get(void);
+int8_t rt_tz_is_dst(void);
+#endif /* RT_LIBC_USING_LIGHT_TZ_DST */
+
+struct itimerspec;
+
 #if defined(_GNU_SOURCE) && (defined(__x86_64__) || defined(__i386__))
 /* linux x86 platform gcc use! */
 #define _TIMEVAL_DEFINED
@@ -218,11 +216,6 @@ int timer_gettime(timer_t timerid, struct itimerspec *its);
 int timer_settime(timer_t timerid, int flags, const struct itimerspec *value, struct itimerspec *ovalue);
 #endif /* RT_USING_POSIX_TIMER */
 
-/* timezone */
-void tz_set(int8_t tz);
-int8_t tz_get(void);
-int8_t tz_is_dst(void);
-
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */