Deprecated CMake function `test_big_endian` used

[jakirkham]

Currently the CMakeLists.txt here makes use of test_big_endian:

dmlc-core/CMakeLists.txt

Lines 166 to 173 in 1334185

	# Check endianness
	include(TestBigEndian)
	test_big_endian(BIG_ENDIAN)
	if(BIG_ENDIAN)
	set(DMLC_CMAKE_LITTLE_ENDIAN 0)
	else()
	set(DMLC_CMAKE_LITTLE_ENDIAN 1)
	endif()

---

However according to the CMake documentation, this is deprecated:

Deprecated since version 3.20: Supserseded by the CMAKE_<LANG>_BYTE_ORDER variable.