On macOS, the system `ar` doesn't support the `D` modifier.
It causes `illegal option -- D` to be emitted as `cargo:warning=`
during the probe.

Add a `run_silent_on_error()` helper that buffers stderr
and only forwards it when the command succeeds.

Repro script:

```bash
#!/usr/bin/env bash
# Reproduce the "illegal option -- D" cargo:warning= issue on macOS.
# Requires macOS system ar (which does not support the D modifier).
set -euo pipefail

DIR=$(mktemp -d)
trap 'rm -rf "$DIR"' EXIT

mkdir -p "$DIR/src"

cat > "$DIR/Cargo.toml" <<'TOML'
[package]
name = "cc-repro"
version = "0.0.0"
edition = "2021"

[build-dependencies]
#cc = { path = "/path/local/cc-rs" }
cc = "=1.2.59"
TOML

echo 'fn main() {}' > "$DIR/src/main.rs"
echo 'void foo(void) {}' > "$DIR/foo.c"
echo 'fn main() { cc::Build::new().file("foo.c").compile("foo"); }' > "$DIR/build.rs"

echo "==> Building in $DIR ..."
cd "$DIR"
OUTPUT=$(cargo build 2>&1)

if echo "$OUTPUT" | grep -qi "illegal option"; then
    echo "BUG: found spurious 'illegal option' warning:"
    echo "$OUTPUT" | grep -i "illegal option"
    exit 1
else
    echo "OK: no spurious warnings."
fi
```

Strip trailing `\r` after splitting on `\n`.
This kinda matches how `str::lines()` handles line endings in std.

ref: https://github.com/rust-lang/rust/blob/bcded331651b60/library/core/src/str/mod.rs#L1309-L1311