Can't use capability as a feature?

[nazar-pc]

I was trying to do this:

#[cfg(all(target_arch = "spirv", not(target_feature = "Int64")))]

And despite I see similar code in spirv-std, I'm getting a warning:

  warning: unexpected `cfg` condition value: `Int64`
    --> ../src/shader.rs:13:15
     |
  13 | #[cfg(all(not(target_feature = "Int64")))]
     |               ^^^^^^^^^^^^^^^^^^^^^^^^
     |
     = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `amx-bf16`, `amx-complex`, `amx-fp16`, `amx-int8`, `amx-tile`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, and `avx512vpopcntdq` and 251 more
     = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
     = note: `#[warn(unexpected_cfgs)]` on by default

I would have expected it to be recognized. Or is it recognized by the backend, but Rust will still complain about it?
This is not happening for target_arch = "spirv" though, which is why I'm confused.