Remove installation instructions for discontinued Funtoo Linux

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

@@ -212,13 +212,6 @@ cave resolve -x repository/rust
 cave resolve -x hyperfine
 ```
 
-### On Funtoo Linux
-
-On Funtoo Linux, hyperfine can be installed [from core-kit](https://github.com/funtoo/core-kit/tree/1.4-release/app-benchmarks/hyperfine):
-```
-emerge app-benchmarks/hyperfine
-```
-
 ### On NixOS
 
 On NixOS, hyperfine can be installed [from the official repositories](https://nixos.org/nixos/packages.html?query=hyperfine):