CICD.yml: Use unshare for run_df_with_masked_proc

[oech3]

Needed to run

coreutils/tests/by-util/test_df.rs

Lines 1095 to 1125 in 4b5a2af

	/// Run df inside a mount namespace where /proc is masked with tmpfs.
	/// Returns (success, stdout, stderr).
	#[cfg(target_os = "linux")]
	fn run_df_with_masked_proc(args: &str) -> Option<(bool, String, String)> {
	use std::process::Command;
	// Check if user namespaces are available
	if !Command::new("unshare")
	.args(["-rm", "true"])
	.status()
	.is_ok_and(|s| s.success())
	{
	return None;
	}
	let df_path = TestScenario::new("df").bin_path.clone();
	let output = Command::new("unshare")
	.args(["-rm", "sh", "-c"])
	.arg(format!(
	"mount -t tmpfs tmpfs /proc && {} df {args}",
	df_path.display()
	))
	.output()
	.ok()?;
	Some((
	output.status.success(),
	String::from_utf8_lossy(&output.stdout).to_string(),
	String::from_utf8_lossy(&output.stderr).to_string(),
	))
	}

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.
Congrats! The gnu test tests/printf/printf-surprise is now passing!
Note: The gnu test tests/env/env-signal-handler was skipped on 'main' but is now failing.

[oech3]

Hmm... the test was already PASS without this. Does it always PASS when unshare is not available?

[cakebaker]

@oech3 if unshare fails, None is returned on line 1107 in the snippet above. And based on that, the asserts in test_df_masked_proc_fallback are not run and so they can't fail.

[oech3]

@cakebaker Thankyou. We should show skip at https://github.com/uutils/coreutils/actions/runs/25249576549/job/74039602884?pr=12120#step:17:2191 instead of ok.

[cakebaker]

@oech3 I think it is not possible to do a skip at runtime.

[oech3]

So it is difficult verify this PR and add tests depending on unshare and strace...
rust-lang/rust#68007

[oech3]

@cakebaker We can catch regression if unshare succeed. Right? If so, I think it is worth to consider merging this.