Merge bitcoin/bitcoin#30380: lint: Ignore files ignored by git in the Markdown Link Checker

dea7afd lint: remove unneeded trailing line fix (willcl-ark)
4d94254 lint: ignore files ignored by git in mlc (willcl-ark)

Pull request description:

  Updating to MLC v0.18.0 includes a new feature which will ignore all files ignored by git: `mlc --gitignore`.

  This helps avoid false-positives flagged by this linter in non-project files, such as a developer might expect to have in their working directory (e.g. guix-builds, python venvs, etc.)

Top commit has no ACKs.

Tree-SHA512: 1752448e0c85abd3c73570a17cc69294de2248d7773c6499833ae33806f6c03f3f345261aa7b855a557b45982fbdcb8190e758d087c43b4fb0254fbb39173432

Author: fanquake

ci/lint/04_install.sh

@@ -58,7 +58,7 @@ curl -sL "https://github.com/koalaman/shellcheck/releases/download/${SHELLCHECK_
     tar --xz -xf - --directory /tmp/
 mv "/tmp/shellcheck-${SHELLCHECK_VERSION}/shellcheck" /usr/bin/
 
-MLC_VERSION=v0.16.3
+MLC_VERSION=v0.18.0
 MLC_BIN=mlc-x86_64-linux
 curl -sL "https://github.com/becheran/mlc/releases/download/${MLC_VERSION}/${MLC_BIN}" -o "/usr/bin/mlc"
 chmod +x /usr/bin/mlc

test/lint/test_runner/src/main.rs

@@ -410,6 +410,7 @@ fn lint_markdown() -> LintResult {
         "--offline",
         "--ignore-path",
         md_ignore_path_str.as_str(),
+        "--gitignore",
         "--root-dir",
         ".",
     ])
@@ -419,11 +420,6 @@ fn lint_markdown() -> LintResult {
         Ok(output) if output.status.success() => Ok(()),
         Ok(output) => {
             let stderr = String::from_utf8_lossy(&output.stderr);
-            let filtered_stderr: String = stderr // Filter out this annoying trailing line
-                .lines()
-                .filter(|&line| line != "The following links could not be resolved:")
-                .collect::<Vec<&str>>()
-                .join("\n");
             Err(format!(
                 r#"
 One or more markdown links are broken.
@@ -433,7 +429,7 @@ Relative links are preferred (but not required) as jumping to file works nativel
 Markdown link errors found:
 {}
                 "#,
-                filtered_stderr
+                stderr
             ))
         }
         Err(e) if e.kind() == ErrorKind::NotFound => {