The legacy version of the driver is failing to build on Debian with Hurd kernel with the following error:

src/mongo/platform/random.cpp:157:2: error: #error Must implement SecureRandom for platform

As far as I know Debian Hurd has /dev/urandom and it sould be possible to detect it using _gnu_hurd_ macro (not tested yet, as I do not have direct access to an hurd installation at the moment).