llvm: fix use of invalid alignment

* Initialize `big_align` with 1 as 0 is not a valid alignment.
 * Add an assert to `alignForwardGeneric` to catch this issue earlier.
 * Refactor valid alignment checks to call a more descriptive function.
52e5c66025Jacob Young committed on 12/19/2022, 3:11:26 AMparent18f0566
2 files changedLine totals unavailable