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, DMLC-Core makes this choice by manually editing raw build flags:

dmlc-core/CMakeLists.txt

Lines 200 to 211 in 1ef6649

	if(MSVC)
	target_compile_definitions(dmlc PUBLIC -DDMLC_USE_CXX11=1)
	if(NOT BUILD_SHARED_LIBS AND NOT DMLC_FORCE_SHARED_CRT)
	foreach(flag_var
	CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
	CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
	if(${flag_var} MATCHES "/MD")
	string(REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")
	endif(${flag_var} MATCHES "/MD")
	endforeach(flag_var)
	endif()
	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc")

This approach is brittle and prone to errors.

A more robust method is to use the built-in flag CMAKE_MSVC_RUNTIME_LIBRARY to control the linking mode for the MSVC runtime.