Implement interrupt handling for long-running commands and archive extraction

- Added an `interrupts` module to manage Ctrl-C signals and propagate them to child processes.
- Refactored archive extraction functions to check for interrupts and handle them gracefully.
- Introduced `copy_interruptibly` function to allow for interruptible copying of data.
- Updated various source files to utilize the new interrupt handling functions, ensuring that commands and archive extractions can be interrupted by the user.
- Added tests to verify the interrupt functionality during copying and tar extraction.
- Introduced a new Meson option for generating HTML CLI documentation.
- Enhanced the `PackageSpec` struct to support additional Rust LTO flags.

src/source/mod.rs

@@ -296,6 +296,7 @@ pub fn prepare(spec: &PackageSpec, cache_dir: &Path, build_dir: &Path) -> Result
     let mut primary: Option<PathBuf> = None;
 
     for (idx, src) in spec.sources().iter().enumerate() {
+        crate::interrupts::check()?;
         let src_dir = prepare_one(spec, src, cache_dir, build_dir)
             .with_context(|| format!("Failed to prepare source #{}", idx + 1))?;
         if idx == 0 {
@@ -409,6 +410,7 @@ fn prepare_one(
 fn copy_dir_recursive(src: &Path, dst: &Path) -> Result<()> {
     fs::create_dir_all(dst)?;
     for entry in WalkDir::new(src) {
+        crate::interrupts::check()?;
         let entry = entry?;
         let rel = entry.path().strip_prefix(src).unwrap();
         let target = dst.join(rel);