Describe the Linux cache-clearing example accurately

Replace `println!` calls on the results paths with `writeln!` on
`io::stdout()` and propagate the `io::Error` to `main`, where
`ErrorKind::BrokenPipe` is turned into a quiet `exit(0)`. This matches
the conventional behavior of command-line tools when their output pipe
is closed early (e.g. `hyperfine ... | head -n 0`), and fixes panics in
all run-output paths: the per-benchmark header and results, the speed
comparison summary, and `-`-style exports to stdout. The warnings and
"Note" outputs to stderr are converted the same way.


---------

Co-authored-by: Mathjk <Mathjk@users.noreply.github.com>
Co-authored-by: David Peter <mail@david-peter.de>

.github/workflows/CICD.yml

@@ -79,6 +79,7 @@ jobs:
       matrix:
         job:
           - { target: aarch64-unknown-linux-gnu   , os: ubuntu-24.04, use-cross: true }
+          - { target: aarch64-unknown-linux-musl  , os: ubuntu-24.04, use-cross: true }
           - { target: arm-unknown-linux-gnueabihf , os: ubuntu-24.04, use-cross: true }
           - { target: arm-unknown-linux-musleabihf, os: ubuntu-24.04, use-cross: true }
           - { target: i686-pc-windows-msvc        , os: windows-2022                  }

README.md

@@ -56,8 +56,8 @@ hyperfine --warmup 3 'grep -R TODO *'
 ```
 
 Conversely, if you want to run the benchmark for a cold cache, you can use the `-p`/`--prepare`
-option to run a special command before *each* timing run. For example, to clear harddisk caches
-on Linux, you can run
+option to run a special command before *each* timing run. For example, to clear Linux filesystem caches,
+you can run
 ```sh
 sync; echo 3 | sudo tee /proc/sys/vm/drop_caches
 ```