I have no idea what libraries freeRTOS provides, except that Wikipedia states "next to nothing". This means you will probably have to implement your own VFS layer to provide file system, locking, timer/sleep and misceallaneous other services. There is some documentation of the VFS layer and some sample code for inserting a "shim VFS" to allow interception and debugging of VFS methods. I am using a test harness shim VFS so that VFS calls are duplicated and results compared between the standard linux VFS and my own VFS. Maybe a similar approach - developing a VFS under linux that pretends to be running under freeRTOS - would work in your case. There are also numerous compile time options to reduce SQlite footprint so that it may run in embedded environments.