Fix clang-tidy job

Explicitly specify versions of clang, clang++ and clang-tidy so we don't
run with mismatched versions.

GitHub seems to have recently bumped the version of clang installed in
its Ubuntu 18.04 runners to version 9, and aliased it to
`/usr/bin/clang` / `/usr/bin/clang++`. But running `apt-get install
clang-tidy` would install an older version of clang-tidy from LLVM _6.0_
at `/usr/bin/clang-tidy`.

See: https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu1804-README.md

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 662f491d050d0e8edd7c17355cbe6e70d8a2448c..07f2904642f7698c999feca2d7af809e6e27db80 100644 (file)
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -267,11 +267,11 @@ jobs:
 
           - name: Clang-Tidy
             os: ubuntu-18.04
-            CC: clang
-            CXX: clang++
+            CC: clang-9
+            CXX: clang++-9
             RUN_TESTS: none
-            CMAKE_PARAMS: -DENABLE_CLANG_TIDY=ON
-            apt_get: libzstd-dev clang-tidy
+            CMAKE_PARAMS: -DENABLE_CLANG_TIDY=ON -DCLANGTIDY=/usr/bin/clang-tidy-9
+            apt_get: libzstd-dev clang-9 clang-tidy-9
 
     steps:
       - name: Get source