unsafe fn find_function(engine: LLVMExecutionEngineRef, name: &str) -> WeldResult<I64Func> {
    let c_name = CString::new(name).unwrap();
    let func_addr = LLVMGetFunctionAddress(engine, c_name.as_ptr());
    if func_addr == 0 {
        return compile_err!("No function named {} in module", name);
    }
    let function: I64Func = mem::transmute(func_addr);
    Ok(function)
}
Get a pointer to a named function in an execution engine.
weld/src/codegen/llvm2/jit.rs