cmSystemTools: Remove unused include <fcntl.h>

We do not seem to need this header anymore, and including it on AIX
causes `#define open open64` which breaks `std::ifstream::open` calls.

Source/cmSystemTools.cxx

@@ -60,8 +60,7 @@
 #endif
 
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#  include <fcntl.h>
-#  include "cmCryptoHash.h"
+# include "cmCryptoHash.h"
 #endif
 
 #if defined(CMAKE_USE_ELF_PARSER)