tests: Fix tests if the HOST triple is too long

The HOST triple defaults to the current host and gets printed in the help output. The CLI tests
currently match it with `[..]`. However, if the triple is too long clap might introduce a line
break, which `[..]` can't handle.
Use `...` instead to match arbitrary lines at the position. Not elegant, but these are just smoke
tests to ensure there's no major probelm. They are not meant to ensure 100% stable output.

Fixes: #226

Author: LingMan

tests/cmd/h.stdout

@@ -15,7 +15,7 @@ Options:
                                 (YYYY-MM-DD), git tag name (e.g. 1.58.0) or git commit SHA.
       --force-install           Force installation over existing artifacts
   -h, --help                    Print help information (use `--help` for more detail)
-      --host <HOST>             Host triple for the compiler [default: [..]]
+...
       --install <INSTALL>       Install the given artifact
       --preserve                Preserve the downloaded artifacts
       --preserve-target         Preserve the target directory used for builds