COMP: Fix cmCTestVC char[]->string Borland warning

The Borland compiler warns about returning a char[] from a function with
return type std::string without an explicit construction.

Source/CTest/cmCTestVC.cxx

@@ -86,7 +86,7 @@ std::string cmCTestVC::GetNightlyTime()
           t->tm_hour,
           t->tm_min,
           t->tm_sec);
-  return current_time;
+  return std::string(current_time);
 }
 
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