For some reason when building with gcc-7.2 (which is default
in previous Ubuntu LTS) the guarded allocator is not being
properly instantiated.
Doesn't happen with newer version of gcc-7 which is 7.3, and
also doesn't happen with gcc-6 and gcc-8.
Would be nice to know what is wrong, but for the time being
committing workaround which keeps Blender users happy.