swift234

SIL: Fix miscompiles with @effects(readonly) functions that have indirect results

When resilience is enabled, some functions in the standard library that
are marked @effects(readonly) now have indirect results.

The SILCombiner pass doesn't handle @effects(readonly) with @out results
correctly, so just disable the optimizations temporarily to avoid a
mis-compile when resilience is enabled.

The LLVM readonly attribute can never be applied to such functions, so
don't set it either.

Should not have an effect when resilience is disabled.