Don't emit landing pads with -Z no-landing-pads

Closes #11647
rustuv: Re-work sockaddr glue to not use malloc

This means we can purge even more C from src/rt!
auto merge of #11636 : alexcrichton/rust/purge-all-the-c, r=brson

This means we can purge even more C from src/rt!
Fix cross-compiled pretty tests

They need to read the metadata of cross-compiled crates, so the pretty things
need to have the right target.
auto merge of #11675 : alexcrichton/rust/fix-snap, r=cmr

They need to read the metadata of cross-compiled crates, so the pretty things
need to have the right target.
auto merge of #11653 : alexcrichton/rust/issue-11647, r=luqmana

Closes #11647