run clippy on 3 major platforms

Author: nyurik

.github/workflows/ci.yaml

@@ -30,8 +30,11 @@ jobs:
         run: ./ci/style.sh
 
   clippy:
-    name: Clippy check
-    runs-on: ubuntu-24.04
+    name: Clippy on ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-24.04, macos-14, windows-2022]
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 10
     steps:
       - uses: actions/checkout@v4
@@ -299,7 +302,8 @@ jobs:
       - verify_build
       - ctest_msrv
       - docs
-    # Github branch protection is exceedingly silly and treats "jobs skipped because a dependency
+      - clippy
+    # GitHub branch protection is exceedingly silly and treats "jobs skipped because a dependency
     # failed" as success. So we have to do some contortions to ensure the job fails if any of its
     # dependencies fails.
     if: always() # make sure this is never "skipped"