After setting up the .cargo/config.toml,
and installing the rust source using
`rustup component add rust-src`
I was supposed to rerun the build command `cargo build --target x86_64-oubre_os.json`
this was supposed to compile the code since we now recompiled
`core` and `compiler-builtins` but it didn't succeed,

====================
I got the same error
====================
`
cargo build --target x86_64-oubre_os.json
warning: unused manifest key: package.author
   Compiling oubre_os v0.1.0 (/Users/Starlet/Dev/oubre_os)
error[E0463]: can't find crate for `core`
  |
  = note: the `x86_64-oubre_os` target may not be installed
  = help: consider downloading the target with `rustup target add x86_64-oubre_os`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

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

error[E0463]: can't find crate for `core`
 --> src/main.rs:7:5
  |
7 | use core::panic::PanicInfo;
  |     ^^^^ can't find crate
  |
  = note: the `x86_64-oubre_os` target may not be installed
  = help: consider downloading the target with `rustup target add x86_64-oubre_os`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

error: requires `sized` lang_item

For more information about this error, try `rustc --explain E0463`.
error: could not compile `oubre_os` due to 4 previous errors
`
============================
Using this tutorial,
https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-std
============================
I ran
`cargo +nightly run -Z build-std --target x86_64-oubre_os.json`

and got this output, the compilation was successful, or atleast, it seems so.

warning: unused manifest key: package.author
  Downloaded getopts v0.2.21
  Downloaded unicode-width v0.1.10
  Downloaded compiler_builtins v0.1.85
  Downloaded cc v1.0.76
  Downloaded 4 crates (265.1 KB) in 2.58s
   Compiling compiler_builtins v0.1.85
   Compiling core v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/core)
   Compiling libc v0.2.138
   Compiling cc v1.0.76
   Compiling memchr v2.5.0
   Compiling std v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/std)
   Compiling unwind v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/unwind)
   Compiling rustc-std-workspace-core v1.99.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/rustc-std-workspace-core)
   Compiling alloc v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc)
   Compiling cfg-if v1.0.0
   Compiling adler v1.0.2
   Compiling rustc-demangle v0.1.21
   Compiling rustc-std-workspace-alloc v1.99.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/rustc-std-workspace-alloc)
   Compiling panic_unwind v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/panic_unwind)
   Compiling panic_abort v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/panic_abort)
   Compiling gimli v0.26.1
   Compiling std_detect v0.1.5 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/stdarch/crates/std_detect)
   Compiling miniz_oxide v0.5.3
   Compiling hashbrown v0.12.3
   Compiling object v0.29.0
   Compiling addr2line v0.17.0
   Compiling proc_macro v0.0.0 (/Users/Starlet/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/proc_macro)
   Compiling oubre_os v0.1.0 (/Users/Starlet/Dev/oubre_os)
    Finished dev [unoptimized + debuginfo] target(s) in 32.72s
     Running `target/x86_64-oubre_os/debug/oubre_os`
target/x86_64-oubre_os/debug/oubre_os: target/x86_64-oubre_os/debug/oubre_os: cannot execute binary file


===========
[EDIT]
===========

NOW `cargo build --target x86_64-oubre_os.json` is working.
There was a little typo in the
.cargo/config.toml

I typed `ustable` instead of `unstable`  - WHEWWW

running it now prints,
`
warning: unused manifest key: package.author
   Compiling oubre_os v0.1.0 (/Users/Starlet/Dev/oubre_os)
    Finished dev [unoptimized + debuginfo] target(s) in 0.77s
`