ci: support clang

Ubuntu 22.04 have clang 14 by default, which partially supports
consteval - it fails tntcxx build.

.github/actions/build-tntcxx/action.yml

@@ -9,7 +9,6 @@ inputs:
     default: 'false'
   cxx-standard:
     desciption: 'Corresponds to CMAKE_CXX_STANDARD option of CMake'
-    default: 17
 
 runs:
   using: "composite"

.github/workflows/reusable-testing.yml

@@ -12,6 +12,9 @@ on:
       cxx-standard:
         required: false
         type: number
+      compiler:
+        default: gcc
+        type: string
       use-valgrind:
         default: false
         type: boolean
@@ -36,6 +39,9 @@ jobs:
         run: sudo apt update && sudo apt install -y valgrind
 
       - name: Build tntcxx
+        env:
+          CC: ${{ inputs.compiler }}
+          CXX: ${{ inputs.compiler == 'gcc' && 'g++' || 'clang++' }}
         uses: ./.github/actions/build-tntcxx
         with:
           build-type: ${{ inputs.build-type }}

.github/workflows/testing.yml

@@ -18,16 +18,24 @@ jobs:
           - ubuntu-22.04
           - macos-11
           - macos-12
+        compiler:
+          - gcc
+          - clang
         build-type:
           - Debug
           - RelWithDebInfo
         cxx-standard:
           - 17
           - 20
+        exclude:
+          - runs-on: ubuntu-22.04
+            compiler: clang
+            cxx-standard: 20
     with:
       runs-on: ${{ matrix.runs-on }}
       build-type: ${{ matrix.build-type }}
       cxx-standard: ${{ matrix.cxx-standard }}
+      compiler: ${{ matrix.compiler }}
 
   valgrind:
     uses: ./.github/workflows/reusable-testing.yml