**Explanation**: We would like untyped throws to be available in Embedded Swift when system allocator is available.
**Scope**: limited to Embedded Swift.
**Risk**: low due to isolated scope, additive nature of the change, and no adoption of untyped throws in Embedded Swift so far.
**Testing**: added new lit tests.
**Issue**: rdar://171325402
These are tests that fail in the next commit without this flag. This
does not add -verify-ignore-unrelated to all tests with -verify, only
the ones that would fail without it. This is NFC since this flag is
currently a no-op.
This is important to get diagnostics for errors which are located in imported modules.
Such errors can sometimes only be detected when building the client module, because the error can be in a generic function which is specialized in the client module.
rdar://151162353