Use CMAKE_MSVC_RUNTIME_LIBRARY to consistently handle linking mode for MSVC runtime

[hcho3]

On the Windows platform, the MSVC (Microsoft Visual C++) runtime can be linked either statically or dynamically. Currently, XGBoost makes this choice by manually editing raw build flags:

xgboost/cmake/Utils.cmake

Lines 29 to 51 in bc6c993

	foreach(variable ${variables})
	if(${variable} MATCHES "/MD")
	string(REGEX REPLACE "/MD" "/MT" ${variable} "${${variable}}")
	set(${variable} "${${variable}}" PARENT_SCOPE)
	endif()
	endforeach()
	set(variables
	CMAKE_CUDA_FLAGS
	CMAKE_CUDA_FLAGS_DEBUG
	CMAKE_CUDA_FLAGS_MINSIZEREL
	CMAKE_CUDA_FLAGS_RELEASE
	CMAKE_CUDA_FLAGS_RELWITHDEBINFO
	)
	foreach(variable ${variables})
	if(${variable} MATCHES "-MD")
	string(REGEX REPLACE "-MD" "-MT" ${variable} "${${variable}}")
	set(${variable} "${${variable}}" PARENT_SCOPE)
	endif()
	if(${variable} MATCHES "/MD")
	string(REGEX REPLACE "/MD" "/MT" ${variable} "${${variable}}")
	set(${variable} "${${variable}}" PARENT_SCOPE)
	endif()
	endforeach()

This approach is brittle and prone to weird breakage, especially when XGBoost is used by a downstream project.

A more robust method is to use the built-in flag CMAKE_MSVC_RUNTIME_LIBRARY to control the linking mode for the MSVC runtime. See https://github.com/dmlc/treelite/blob/260a5d2c22830ec2bdaa5fc6dc186aa6f3b551e7/CMakeLists.txt#L46-L54 for an example.