We currently set the cppdef that indicates which allocator we are using as an env variable in each Sconscript file that needs the information (right now, that is util/, and we are about to add it into db/).

It may make more sense to set this in the config.h file, and define it once in the root Sconscript, rather than making anyone who wants this information alter their Sconscript env to include the ifdef.