Update musl to 1.1.22.

Update musl to 1.1.22.

This is the latest available version. I noticed Rust wasn't using the
latest version when I attempted to have Cargo link object files produced
outside of Cargo / Rust's toolchain and was getting missing symbol
errors. Those missing symbols were added in 1.1.21 and 1.1.22.

I'm not fully sure of the implications of this change or how
comprehensive the test coverage is. Upstream changes in 1.1.21 and
1.1.22 can be found at
https://git.musl-libc.org/cgit/musl/tree/WHATSNEW?h=v1.1.22&id=e97681d6f2c44bf5fa9ecdd30607cb63c780062e#n1989.