Clean between runs in the make parameter-scan example

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                  }

doc/hyperfine.1

@@ -141,7 +141,7 @@ string '{\fIVAR\fP}' in each command by the current parameter value.
 .RS
 Example:
 .RS
-\fBhyperfine\fR \fB\-P\fR threads 1 8 'make \-j {threads}'
+\fBhyperfine\fR \fB\-\-prepare\fR 'make clean' \fB\-P\fR threads 1 8 'make \-j {threads}'
 .RE
 .RE
 .IP

src/cli.rs

@@ -161,7 +161,7 @@ fn build_command() -> Command {
                 .help(
                     "Perform benchmark runs for each value in the range MIN..MAX. Replaces the \
                      string '{VAR}' in each command by the current parameter value.\n\n  \
-                     Example:  hyperfine -P threads 1 8 'make -j {threads}'\n\n\
+                     Example:  hyperfine --prepare 'make clean' -P threads 1 8 'make -j {threads}'\n\n\
                      This performs benchmarks for 'make -j 1', 'make -j 2', …, 'make -j 8'.\n\n\
                      To have the value increase following different patterns, use shell arithmetics.\n\n  \
                      Example: hyperfine -P size 0 3 'sleep $((2**{size}))'\n\n\