arch: add big endian regression test

This was reported along with the fact that memchr 2.7.3 broke big endian
targets. While I at first thought the test suite just somehow missed the
regression and thus this test was somehow novel in some interesting way,
it turned out it was just a CI configuration failure. The existing tests
catch the regression easily (dozens of test failures). The problem, as
mentioned in the previous commit, was that tests in CI weren't using
`cross` when cross compilation was enabled.

So while this test is seemingly redundant, I still think it's good form
to add it.

Ref #152

src/arch/all/memchr.rs

@@ -1143,7 +1143,24 @@ mod tests {
         assert_eq!(4, count);
     }
 
-    /// Generate 500K values.
+    // A test[1] that failed on some big endian targets after a perf
+    // improvement was merged[2].
+    //
+    // At first it seemed like the test suite somehow missed the regression,
+    // but in actuality, CI was not running tests with `cross` but instead with
+    // `cargo` specifically. This is because those steps were using `cargo`
+    // instead of `${{ env.CARGO }}`. So adding this regression test doesn't
+    // really help catch that class of failure, but we add it anyway for good
+    // measure.
+    //
+    // [1]: https://github.com/BurntSushi/memchr/issues/152
+    // [2]: https://github.com/BurntSushi/memchr/pull/151
+    #[test]
+    fn regression_big_endian1() {
+        assert_eq!(One::new(b':').find(b"1:23"), Some(1));
+    }
+
+    // Generate 500K values.
     fn special_values() -> impl Iterator<Item = usize> {
         fn all_bytes() -> impl Iterator<Item = u8> {
             0..=0xff