I managed to build it with MSVC.  But none of the <cxxflags> arguments worked so I had to them all out of the configuration file.  

I built it with the "--layout=versioned" setting, but when I tried to build Jinja2Cpp again by specifying -DBOOST_ROOT=C:/boost_msvc/include/boost-1_69 because the header files are inside the "boost" directory at that location (I think this is a weird installation directory path for Boost, though), CMake still couldn't find Boost.  I looked in FindBoost.cmake module before and saw that there's code in there for finding Boost version 1.69.0 as well, so I don't know why it's not working.  

Jinja2Cpp has Boost in the submodules (the code is all on GitHub), but the version of Boost that they have is 1.64.  I wonder if that's why it can't find 1.69.  Could be that the version in the submodule is too old.