miri fails on chacha20 with incorrectly gated Intel intrinsic #579

error: Undefined Behavior: calling a function that requires unavailable target features: sse4.1
   --> /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/chacha20-0.10.1/src/backends/sse2.rs:133:22
    |
133 |     core.state[13] = _mm_extract_epi32(backend.v[3], 1) as u32;
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: this is on thread `timestamp::cont`
    = note: stack backtrace:
            0: chacha20::backends::sse2::rng_inner::<chacha20::R12, chacha20::variants::Legacy>
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/chacha20-0.10.1/src/backends/sse2.rs:133:22: 133:56
            1: chacha20::rng::<impl rand::rand_core::block::Generator for chacha20::ChaChaCore<chacha20::R12, chacha20::variants::Legacy>>::generate
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/chacha20-0.10.1/src/rng.rs:76:33: 76:80
            2: <rand::rngs::thread::ReseedingCore as rand::rand_core::block::Generator>::generate
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.10.2/src/rngs/thread.rs:56:9: 56:37
            3: rand::rand_core::block::BlockRng::<rand::rngs::thread::ReseedingCore>::next_u64_from_u32
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand_core-0.10.1/src/block.rs:258:13: 258:50
            4: <rand::prelude::ThreadRng as rand::TryRng>::try_next_u64
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.10.2/src/rngs/thread.rs:228:12: 228:35
            5: <rand::prelude::ThreadRng as rand::Rng>::next_u64
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand_core-0.10.1/src/lib.rs:78:15: 78:34
            6: rand::distr::integer::<impl rand::distr::Distribution<u64> for rand::distr::StandardUniform>::sample::<rand::prelude::ThreadRng>
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.10.2/src/distr/integer.rs:52:9: 52:23
            7: <rand::prelude::ThreadRng as rand::RngExt>::random::<u64>
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.10.2/src/rng.rs:97:9: 97:37
            8: rand::random::<u64>
                at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.10.2/src/lib.rs:194:5: 194:19
            9: <rng::imp::RngImp as rng::Rng>::u64
                at src/rng.rs:40:13: 40:27
            10: rng::u64
                at src/rng.rs:14:5: 14:23
            11: timestamp::context::v7_support::Counter::reseed
                at src/timestamp.rs:933:44: 933:61
            12: <timestamp::context::v7_support::ContextV7 as timestamp::ClockSequence>::generate_timestamp_sequence
                at src/timestamp.rs:836:31: 836:75
            13: <&timestamp::context::v7_support::ContextV7 as timestamp::ClockSequence>::generate_timestamp_sequence
                at src/timestamp.rs:466:9: 466:68
            14: timestamp::Timestamp::from_unix::<u64, &timestamp::context::v7_support::ContextV7>
                at src/timestamp.rs:112:13: 112:71
            15: timestamp::context::v7_support::tests::context
                at src/timestamp.rs:1076:27: 1076:80
            16: timestamp::context::v7_support::tests::context::{closure#0}
                at src/timestamp.rs:1070:25: 1070:25