Rust build error: unknown `--json` option `future-incompat` - rust

Question

I am trying to build a basic application for the Adafruit CLUE using Rust.
When using the peripheral access crate (PAC) everything works fine, but I would like to use the HAL crate from Nordic Semiconductors.
I set up a very basic project which uses their nrf52840-hal crate. When running cargo build, I get the following error (full build log with --verbose):
Updating crates.io index
Compiling semver-parser v0.7.0
Compiling cortex-m v0.7.4
Compiling proc-macro2 v1.0.37
Compiling nb v1.0.0
Compiling unicode-xid v0.2.3
Compiling syn v1.0.92
Compiling vcell v0.1.3
Compiling void v1.0.2
Compiling bitfield v0.13.2
Compiling cortex-m-rt v0.7.1
Compiling critical-section v0.2.7
Compiling typenum v1.15.0
info: syncing channel updates for 'nightly-2021-08-18-x86_64-unknown-linux-gnu'
Compiling az v1.2.0
Compiling nrf52840-pac v0.11.0
info: latest update on 2021-08-18, rust version 1.56.0-nightly (30a0a9b69 2021-08-17)
Compiling fixed v1.15.0
Compiling cfg-if v1.0.0
info: component 'rust-src' is up to date
info: component 'rust-std' for target 'riscv32imac-unknown-none-elf' is up to date
info: component 'rust-std' for target 'riscv32imc-unknown-none-elf' is up to date
info: component 'rust-std' for target 'thumbv6m-none-eabi' is up to date
info: component 'rust-std' for target 'thumbv7em-none-eabi' is up to date
info: component 'rustfmt' for target 'x86_64-unknown-linux-gnu' is up to date
warning: Force-skipping unavailable component 'rust-std-avr-specs/avr-atmpeg328p.json'
Compiling bare-metal v1.0.0
error: unknown `--json` option `future-incompat`
Compiling half v1.8.2
error: could not compile `critical-section`
warning: build failed, waiting for other jobs to finish...
error: build failed
I am using rustup with the stable toolchain on Ubuntu 20.04 (using nighly 2022-05-03 does not change anything to the error message). Rustup version output is:
rustup 1.24.3 (ce5817a94 2021-05-31)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.60.0 (7737e0b5c 2022-04-04)`
The full project is available here.
My .cargo/config.toml file is:
[build]
target = "thumbv7em-none-eabihf"
rustflags = [
"-C", "link-arg=-Tlink.x",
]
The Cargo.toml is:
[package]
name = "hal-test"
version = "0.1.0"
edition = "2021"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
cortex-m-rt = "0.7.1"
nrf52840-hal = "0.15.0"
panic-halt = "0.2.0"
and the src/main.rs file is:
#![no_std]
#![no_main]
use panic_halt as _;
#[cortex_m_rt::entry]
fn main() -> ! {
loop {}
}
I tried to go through the dependency tree but I failed to find where this future-incompat option is added, given that it is passed plenty of times to rustc and it succeeds.
I would appreciate any pointers as to where to look further.
Update 2022-05-06: building the project with the exact same toolchain version on Ubuntu 21.04 works, I'll have to investigate further.

Answer 1

The issue was fixed by switching away from the rustup snap and using the recommended installation method of running the shell script (https://www.rust-lang.org/tools/install).