Support for the `thumbv4t-none-eabi` target

[kutu-dev]

If I add to my devShell the following package:

(rust-bin.selectLatestNightlyWith (toolchain: toolchain.default.override {
          extensions = [ "rust-src" ];
          targets = [ "thumbv4t-none-eabi" ];
}))

Running nix develop will fail with the error:

       Unknown target `thumbv4t-none-eabi`, typo or not supported by this version?
       note: profile components: rustc cargo rust-std rust-mingw rust-docs rustfmt-preview clippy-preview
       note: selected targets: x86_64-unknown-linux-gnu thumbv4t-none-eabi
       note: selected extensions: rust-src
       note: components available for x86_64-unknown-linux-gnu: cargo clippy clippy-preview llvm-bitcode-linker llvm-bitcode-linker-preview llvm-tools llvm-tools-preview miri miri-preview reproducible-artifacts rust rust-analysis rust-analyzer rust-analyzer-preview rust-docs rust-docs-json rust-docs-json-preview rust-src rust-std rustc rustc-codegen-cranelift rustc-codegen-cranelift-preview rustc-dev rustc-docs rustfmt rustfmt-preview
       note: check here to see all targets and which components are available on each targets:
             https://rust-lang.github.io/rustup-components-history

It looks like thumbv4t-none-eabi is not listed in the targets.nix file.

Is there any fix or workaround?