rust: rust_is_available: support testing with `bash` as `/bin/sh`

`command -v` behaves differently on `dash` vs. `bash` when faced with
a file without the execute bit.

Thus, for the non-executable `rustc` and `bindgen` tests, support both
possible outputs that the script currently gives.

This makes the test script clean on distributions like Fedora.

Reviewed-by: Onur Özkan <work@onurozkan.dev>
Link: https://patch.msgid.link/20260719130723.162899-1-ojeda@kernel.org
[ Added custom assertion message as suggested. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

0 files changed, 0 insertions, 0 deletions