Auto merge of #2044 - JohnTitor:fix-ci, r=JohnTitor
Auto merge of #2044 - JohnTitor:fix-ci, r=JohnTitor

Fix CI on `i686-unknown-linux-musl`

I suspect `focal-20210119` breaks the build, uses an older image to fix the `Could not configure 'libc6:i386'` failure.

rust-lang/libc,rust-lang/libc,rust-lang/libc