Building msgpack gives currently gives the following warning:
"CMake Deprecation Warning at CMakeLists.txt:1 (CMAKE_MINIMUM_REQUIRED):
Compatibility with CMake < 3.5 will be removed from a future version of
CMake.
Update the VERSION argument <min> value or use a ...<max> suffix to tell
CMake that the project does not need compatibility with older versions."
Reuse same solution as fc18087cdfaadec0b905643f93950387e797da08 as the
policy CMP0060 introduced in cmake 3.3 causes problems with when linking
for 32-bit otherwise.
