OptionalauxMutable aux store from flattenFunWithAux. When provided,
collectConcreteArrays(auxStore.value) is called AFTER the trace
(which populates auxStore.value) to protect concrete aux arrays
from PE intermediate disposal.
Must be passed as the store reference — NOT pre-computed arrays —
because auxStore.value is only set during linearizeFlatUtil.
OptionalskipWhen true, skip building the backward jaxpr. The returned pullback
will be a no-op stub. Use for linearizeFlat which only needs the
forward jaxpr.
Options for aotLinearize().