fix CI error (#1187)
fix CI error (#1187)

* fix CI error

This happened because newer versions of Bash (5.x) rightly fail on using
`continue` incorrectly.

I rewrote that section to simply run `rustfmt` if the example is allowed
to compile. I am unsure why that is in a subshell.

As an aside, I tested this locally on macOS by running `brew install
bash`, then changing the shebang to use `/usr/local/bin/bash`.

* cleaner fix for CI failure

See https://github.com/exercism/rust/pull/1187#issuecomment-789894721
exercism/xrust,petertseng/exercism-rust,exercism/xrust,petertseng/exercism-rust,petertseng/exercism-rust