Fix CI build of simd-json

    error[E0308]: mismatched types
       --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/simd-json-0.4.13/src/lib.rs:213:86
        |
    213 | fn please_compile_with_a_simd_compatible_cpu_setting_read_the_simdjonsrs_readme() -> ! {}
        |    ----------------------------------------------------------------------------      ^ expected `!`, found `()`
        |    |
        |    implicitly returns `()` as its body has no tail or `return` expression
        |
        = note:   expected type `!`
                found unit type `()`

Author: dtolnay

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ on:
   schedule: [cron: "40 1 * * *"]
 
 env:
-  RUSTFLAGS: '-Dwarnings'
+  RUSTFLAGS: -C target-cpu=native -Dwarnings
 
 jobs:
   test: