HAL_Linux: Add set_system_clock

libraries/AP_HAL_Linux/Util.cpp

@@ -5,6 +5,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <errno.h>
+#include <time.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -50,4 +51,13 @@ void LinuxUtil::_toneAlarm_timer_tick(){
     }
     
 }
+
+void LinuxUtil::set_system_clock(uint64_t time_utc_usec)
+{
+    timespec ts;
+    ts.tv_sec = time_utc_usec/1.0e6;
+    ts.tv_nsec = (time_utc_usec % 1000000) * 1000;
+    clock_settime(CLOCK_REALTIME, &ts);    
+}
+
 #endif // CONFIG_HAL_BOARD == HAL_BOARD_LINUX

libraries/AP_HAL_Linux/Util.h

@@ -26,6 +26,11 @@ public:
     
     void _toneAlarm_timer_tick();
 
+    /*
+      set system clock in UTC microseconds
+     */
+    void set_system_clock(uint64_t time_utc_usec);
+
 private:
 	static Linux::ToneAlarm _toneAlarm;
     int saved_argc;