TWRP: Added TW_CLOCK_OFFSET flag to further adjust the clock.

For devices with the Qualcomm RTC fix whose clocks need further tuning
such as the LG V20 whose ats files produces the correct time except 
46 years in the future.

Takes adjustment in seconds and adjusts after reading the the ats file.

Boardconfig.mk
TW_CLOCK_OFFSET := -1451606400

Change-Id: I0b2d35dd0026ed18a7bbebf683517f7c0eaa53ff
diff --git a/twrp-functions.cpp b/twrp-functions.cpp
index f82de61..11e745b 100644
--- a/twrp-functions.cpp
+++ b/twrp-functions.cpp
@@ -996,6 +996,10 @@
 	gettimeofday(&tv, NULL);
 
 	tv.tv_sec += offset/1000;
+#ifdef TW_CLOCK_OFFSET
+// Some devices are even quirkier and have ats files that are offset from the actual time
+	tv.tv_sec = tv.tv_sec + TW_CLOCK_OFFSET;
+#endif
 	tv.tv_usec += (offset%1000)*1000;
 
 	while (tv.tv_usec >= 1000000)