Rollup merge of #131941 - lolbinarycat:compiletest-need-html-tidy, r=…

…clubby789

compiletest: disambiguate html-tidy from rust tidy tool

when i first saw this error message i was very confused, i thought it was talking about `src/tools/tidy`.  now it should be much more clear what tool should be installed.

src/tools/compiletest/src/main.rs

@@ -19,7 +19,7 @@ fn main() {
     let config = Arc::new(parse_config(env::args().collect()));
 
     if !config.has_tidy && config.mode == Mode::Rustdoc {
-        eprintln!("warning: `tidy` is not installed; diffs will not be generated");
+        eprintln!("warning: `tidy` (html-tidy.org) is not installed; diffs will not be generated");
     }
 
     if !config.profiler_runtime && config.mode == Mode::CoverageRun {