CTest: use std::chrono::steady_clock for time keeping

It was reported in issue #17345 that CTest does not use monotonic time
to report test duration. Monotonic clocks are not affected by large NTP
adjustments or things like daylight savings time.

As CMake 3.10 requires C++11, which introduced std::chrono, this commit
moves the time keeping in CTest from cmSystemTools::GetTime() to
std::chrono::steady_clock.

Fixes: #17345

1 files changed, 3 insertions, 1 deletions

diff --git a/Source/CTest/cmCTestScriptHandler.h b/Source/CTest/cmCTestScriptHandler.h
index b6cd97b..2090d04 100644
--- a/Source/CTest/cmCTestScriptHandler.h
+++ b/Source/CTest/cmCTestScriptHandler.h
@@ -7,6 +7,7 @@
 
 #include "cmCTestGenericHandler.h"
 
+#include <chrono>
 #include <string>
 #include <vector>
 
@@ -104,6 +105,7 @@ public:
 
   void CreateCMake();
   cmake* GetCMake() { return this->CMake; }
+
 private:
   // reads in a script
   int ReadInScript(const std::string& total_script_arg);
@@ -156,7 +158,7 @@ private:
   double ContinuousDuration;
 
   // what time in seconds did this script start running
-  double ScriptStartTime;
+  std::chrono::steady_clock::time_point ScriptStartTime;
 
   cmMakefile* Makefile;
   cmGlobalGenerator* GlobalGenerator;