A lot of attributes are essentially default target configuration, and we should only differ when there's a good reason to.
For the attributes we were already setting:
- the ptrauth and target CPU/feature attributes are taken care of by Clang
- I've updated the optsize/minsize attributes to the apparent intent
- I've left the frame-pointer override in place for now
Fixes rdar://63289339, which was caused by Swift's ptrauth IR attributes getting out of sync with Clang's.
