Back out 89d57ffb: "build: add rust-toolchain.toml"

This backs out commit 89d57ffb29.

This is causing a CI failure because we can't build musl binaries,
presumably because the rust-toolchain file overriding the chosen
musl toolchain for some reason. Backout until we can reapply
a proper fix.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

Cargo.toml

@@ -7,7 +7,7 @@ members = ["cli", "lib", "lib/gen-protos", "lib/proc-macros", "lib/testutils"]
 [workspace.package]
 version = "0.24.0"
 license = "Apache-2.0"
-rust-version = "1.76" # NOTE: remember to update CI, rust-toolchain.toml, contributing.md, changelog.md, install-and-setup.md, and flake.nix
+rust-version = "1.76" # NOTE: remember to update CI, contributing.md, changelog.md, install-and-setup.md, and flake.nix
 edition = "2021"
 readme = "README.md"
 homepage = "https://github.com/martinvonz/jj"

docs/contributing.md

@@ -133,13 +133,16 @@ recommended steps.
 One-time setup:
 
     rustup toolchain add nightly  # wanted for 'rustfmt'
-    cargo install cargo-insta cargo-watch cargo-nextest
+    rustup toolchain add 1.76     # also specified in Cargo.toml
+    cargo install cargo-insta
+    cargo install cargo-watch
+    cargo install cargo-nextest
 
 During development (adapt according to your preference):
 
     cargo watch --ignore '.jj/**' -s \
       'cargo clippy --workspace --all-targets \
-       && cargo check --workspace --all-targets'
+       && cargo +1.76 check --workspace --all-targets'
     cargo +nightly fmt # Occasionally
     cargo nextest run --workspace # Occasionally
     cargo insta test --workspace --test-runner nextest # Occasionally
@@ -186,17 +189,6 @@ These are listed roughly in order of decreasing importance.
    On Linux, you may be able to speed up `nextest` even further by using
    the `mold` linker, as explained below.
 
-### Using an alternative Rust compiler version
-
-To use a different version of the Rust compiler/toolchain for development, you
-can run:
-
-    rustup override set 1.80  # or any other version
-
-Or manually set it in individual `cargo` commands:
-
-    cargo +1.80 clippy --workspace --all-targets  # or any other version
-
 ### Using `mold` for faster tests on Linux
 
 On a machine with a multi-core CPU, one way to speed up

rust-toolchain.toml

@@ -1,4 +0,0 @@
-[toolchain]
-channel = "1.76"
-profile = "default"
-components = ["rust-analyzer"]