Fix build of the packages on Turris 1.x

[operutka]

As mentioned at #6, the build for Turris 1.x devices may be broken.

[BKPepe]

Faillog:

test -e $HOME/.cargo/bin/rustup || turris1x/ws/build/build_dir/hostpkg/rust-lang-1.60.0/rustup-init.sh -y --profile minimal
$HOME/.cargo/bin/rustup toolchain install 1.60.0
info: syncing channel updates for '1.60.0-x86_64-unknown-linux-gnu'

  1.60.0-x86_64-unknown-linux-gnu unchanged - rustc 1.60.0 (7737e0b5c 2022-04-04)

info: checking for self-updates
$HOME/.cargo/bin/rustup target add --toolchain 1.60.0 powerpc-unknown-linux-musl
error: toolchain '1.60.0-x86_64-unknown-linux-gnu' does not contain component 'rust-std' for target 'powerpc-unknown-linux-musl'
note: not all platforms have the standard library pre-compiled: https://doc.rust-lang.org/nightly/rustc/platform-support.html
make[2]: *** [Makefile:48: turris1x/ws/build/build_dir/hostpkg/rust-lang-1.60.0/.built]) Error 1

[BKPepe]

There is a follow-up, it does no longer crash the entirely build, but for Turris 1.x it fails with this:

error[E0463]: can't find crate for `core`
  |
  = note: the `powerpc-unknown-linux-musl` target may not be installed
  = help: consider downloading the target with `rustup target add powerpc-unknown-linux-musl`

error[E0463]: can't find crate for `compiler_builtins`

error[E0463]: can't find crate for `core`
 --> /home/beast/beast/workspace/turris-os-packages-crashlab-turris1x/build/staging_dir/host/lib/cargo/registry/src/github.com-1ecc6299db9ec823/lazy_static-1.4.0/src/inline_lazy.rs:8:1
  |
8 | extern crate core;
  | ^^^^^^^^^^^^^^^^^^ can't find crate
  |
  = note: the `powerpc-unknown-linux-musl` target may not be installed
  = help: consider downloading the target with `rustup target add powerpc-unknown-linux-musl`

error[E0463]: can't find crate for `std`
  |
  = note: the `powerpc-unknown-linux-musl` target may not be installed
  = help: consider downloading the target with `rustup target add powerpc-unknown-linux-musl`

Most likely, it is going to be fixed by this 21d309b but it is not tested, yet.

[operutka]

I plan to look at this issue once #5 and #6 are merged.

[BKPepe]

I can confirm that #11 fixes it and it runs on Turris 1.x routers. Also, I opened pull request with my commit 21d309b to Rust rust-lang/rust#100860 to have this included in upstream.