Rust custom panic_fmt lead to found duplicate lang item `panic_fmt` the lang item is first defined in crate `core`

Question

On an embedded project with Rust, I'm currently facing the following issue when I try to implement my own panic handler.

To give you some context, I'm currently building my project with rust nightly version. The code is here :

#![no_std] //Disable standard lib
#![no_main]
#![feature(lang_items)]

#[lang = "panic_fmt"]
#[lang = "eh_personality"] extern fn eh_personality() {}
#[no_mangle]
pub extern fn panic_fmt(fmt: core::fmt::Arguments, file: &'static str, line: u32) -> ! {
    println!("\n\nPANIC in {} at line {}:", file, line);
    println!("    {}", fmt);
    loop{}
}

Here is partialy my Cargo.toml :

[lib]
crate-type = ["staticlib"]

[dependencies]
multiboot2 = { version = "0.19", default-features = false }
rlibc = "1.0.0"
spin = "0.9.8"
volatile = "0.2.7"
x86_64 = "0.14.11"

[dependencies.lazy_static]
version = "1.4.0"
features = ["spin_no_std"]

and my target :

{
    "llvm-target": "x86_64-unknown-none",
    "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
    "arch": "x86_64",
    "target-endian": "little",
    "target-pointer-width": "64",
    "target-c-int-width": "32",
    "os": "none",
    "executables": true,
    "linker-flavor": "ld.lld",
    "linker": "rust-lld",
    "panic-strategy": "abort",
    "disable-redzone": true,
    "features": "-mmx,-sse,+soft-float"
}

When compiling, I got the following error : panic_fmt lead to found duplicate lang item panic_fmt the lang item is first defined in crate core

I can't figure out why

I tried to take a look on some issues from Rust official repository but nothing is really similar to my case.