use problem matchers for tidy CI

src/ci/docker/host-x86_64/x86_64-gnu-llvm-14/Dockerfile

@@ -62,6 +62,4 @@ ENV SCRIPT ../x.py --stage 2 test --exclude src/tools/tidy && \
            # work.
            #
            ../x.ps1 --stage 2 test tests/ui --pass=check \
-                             --host='' --target=i686-unknown-linux-gnu && \
-           # Run tidy at the very end, after all the other tests.
-           python2.7 ../x.py --stage 2 test src/tools/tidy
+                             --host='' --target=i686-unknown-linux-gnu

src/ci/github-actions/problem_matchers.json

@@ -0,0 +1,15 @@
+{
+    "problemMatcher": [
+        {
+            "owner": "tidy-error-file-line",
+            "pattern": [
+                {
+                    "regexp": "^tidy error: /checkout/(.+):(\\d+): (.+)$",
+                    "file": 1,
+                    "line": 2,
+                    "message": 3
+                }
+            ]
+        }
+    ]
+}

src/ci/scripts/run-build-from-ci.sh

@@ -10,6 +10,8 @@ source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 export CI="true"
 export SRC=.
 
+echo "::add-matcher::src/ci/github-actions/problem_matchers.json"
+
 # Remove any preexisting rustup installation since it can interfere
 # with the cargotest step and its auto-detection of things like Clippy in
 # the environment