target-feature -mma -vsx and -altivec throwing warning for being unstable

We recently added support for rust on powerpc64le and we want mma vsx hard-float and altivec disabled.
We did that but it's throwing warning

  warning: unknown and unstable feature specified for `-Ctarget-feature`: `mma`
    |
    = note: it is still passed through to the codegen backend, but use of this feature might be unsound and the behavior of this feature can change in the future
    = help: consider filing a feature request

  warning: unstable feature specified for `-Ctarget-feature`: `vsx`
    |
    = note: this feature is not stably supported; its behavior can change in the future

  warning: unknown and unstable feature specified for `-Ctarget-feature`: `hard-float`
    |
    = note: it is still passed through to the codegen backend, but use of this feature might be unsound and the behavior of this feature can change in the future
    = help: consider filing a feature request

  warning: unstable feature specified for `-Ctarget-feature`: `altivec`
    |
    = note: this feature is not stably supported; its behavior can change in the future

I tried this with latest linux next with rust for linux on powerpc64le support. Here's a link to the patch series.
https://lore.kernel.org/all/20260708082454.1254320-1-mkchauras@gmail.com/

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rustc --version --verbose:

rustc 1.96.1 (31fca3adb 2026-06-26)
binary: rustc
commit-hash: 31fca3adb283cc9dfd56b49cdee9a96eb9c96ffd
commit-date: 2026-06-26
host: x86_64-unknown-linux-gnu
release: 1.96.1
LLVM version: 22.1.2

No source file or test is named. Reproduce on Linux powerpc64le with the reported Rust version and the mma, vsx, hard-float, and altivec target features disabled, then trace how rustc validates these features. Done means the intended configuration no longer produces inappropriate unknown or unstable-feature warnings.