CTest: adopt std::chrono::system_clock

After the refactor to make CTest use std::chrono::steady_clock for the
keeping of time for test duration, there are still references to
cmSystemTools::GetTime() left.
To further adopt std::chrono for time related activities, this commit
changes those remaining references to std::chrono::system_clock::now()
calls and alters the storage from either unsigned int or double to
std::chrono::system_clock::time_point.

For ease of conversion, a converter method is added to cmXMLWriter that
converts from a std::chrono::system_clock::time_point to the number of
seconds since the UN*X epoch as that is expected behaviour. This means
no more casts as required.

Functionally should be no difference as the system_clock is implemented
in the same terms.

1 files changed, 2 insertions, 3 deletions

diff --git a/Source/CTest/cmCTestUpdateHandler.cxx b/Source/CTest/cmCTestUpdateHandler.cxx
index 2bd0253..f86d4a3 100644
--- a/Source/CTest/cmCTestUpdateHandler.cxx
+++ b/Source/CTest/cmCTestUpdateHandler.cxx
@@ -177,8 +177,7 @@ int cmCTestUpdateHandler::ProcessHandler()
     return -1;
   }
   std::string start_time = this->CTest->CurrentTime();
-  unsigned int start_time_time =
-    static_cast<unsigned int>(cmSystemTools::GetTime());
+  auto start_time_time = std::chrono::system_clock::now();
   auto elapsed_time_start = std::chrono::steady_clock::now();
 
   bool updated = vc->Update();
@@ -226,7 +225,7 @@ int cmCTestUpdateHandler::ProcessHandler()
   cmCTestOptionalLog(this->CTest, DEBUG, "End" << std::endl, this->Quiet);
   std::string end_time = this->CTest->CurrentTime();
   xml.Element("EndDateTime", end_time);
-  xml.Element("EndTime", static_cast<unsigned int>(cmSystemTools::GetTime()));
+  xml.Element("EndTime", std::chrono::system_clock::now());
   xml.Element("ElapsedMinutes",
               std::chrono::duration_cast<std::chrono::minutes>(
                 std::chrono::steady_clock::now() - elapsed_time_start)