CMake: Fix dashboard test failure

Eliminate the platform difference in calling stat. We call stat normally
in other places in the CMake code base just fine. Works everywhere we
work. Will hopefully also fix the Borland Continuous dashboard failure
that is occurring with respect to correctly measuring the modification
time of a freshly generated file.

Source/cmTimestamp.cxx

@@ -33,16 +33,10 @@ std::string cmTimestamp::CurrentTime(
 std::string cmTimestamp::FileModificationTime(const char* path,
   const std::string& formatString, bool utcFlag)
 {
-#ifdef _WIN32
-  #define STAT _stat
-#else
-  #define STAT stat
-#endif
-
-  struct STAT info;
+  struct stat info;
   std::memset(&info, 0, sizeof(info));
 
-  if(STAT(path, &info) != 0)
+  if(stat(path, &info) != 0)
     {
     return std::string();
     }