pub static CHECKSTYLE: ToolSpecExpand description
Java linter. Emits SARIF 2.1.0 on stdout; its startup banner goes to stderr.
-c is not in command: checkstyle refuses to run without a ruleset and
which one a project uses is exactly what config_files discovers, so the
path is appended by config_flag. Bare, it exits 1 with “Must specify a
config XML”.