Set MSRV to 1.75.0 as shipped by today's Yocto

This inlcludes updating some formatting and pinning backtrace to the latest
version supporting this Rust version.

Author: sirhcel

Cargo.lock

@@ -7,7 +7,8 @@ license = "MIT/Apache-2.0"
 readme = "README.md"
 homepage = "https://github.com/rust-embedded/gpio-utils"
 keywords = ["gpio", "linux", "sysfs_gpio", "cli", "command-line"]
-edition = "2024"
+edition = "2021"
+rust-version = "1.75.0"
 description = """
 Command-line utilities for interacting with GPIOs under Linux
 
@@ -29,6 +30,9 @@ serde_derive = "1.0"
 serde = "1.0"
 uzers = { version = "0.12.1", default-features = false, features = ["cache"] }
 
+# TODO Unpin this dependency after bumping our MSRV beyond 1.75.0.
+backtrace = "=0.3.74"
+
 [[bin]]
 name = "gpio"
 path = "src/main.rs"

Cargo.toml

@@ -9,7 +9,7 @@
 use crate::config::PinConfig;
 use crate::error::*;
 use lazy_static::lazy_static;
-use nix::unistd::{Gid, Uid, chown};
+use nix::unistd::{chown, Gid, Uid};
 use std::fs;
 use std::io::ErrorKind;
 use std::os::unix::fs as unix_fs;