Fix clang-tidy CI: use libc++ for C++23 std::expected support (TICKET_494)

clang-18 does not define __cpp_lib_expected, so libstdc++-14's <expected>
header is effectively empty. Switch clang-tidy to libc++-18 which has full
C++23 support. Fix four headers with missing includes exposed once
clang-tidy can actually parse the code: <concepts> in seqlock.hpp,
<type_traits> in diagnostic.hpp, buffer_pool.hpp in mpsc_queue.hpp,
trailer.hpp in fixt11/session.hpp.

Author: nonassa

.github/workflows/ci.yml

@@ -166,7 +166,7 @@ jobs:
       - name: Install dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y ninja-build clang-tidy-18 clang-18 libstdc++-14-dev
+          sudo apt-get install -y ninja-build clang-tidy-18 clang-18 libc++-18-dev libc++abi-18-dev
 
       - name: Configure
         env:
@@ -183,20 +183,13 @@ jobs:
             -DNFX_ENABLE_LOGGING=OFF \
             -DNFX_ENABLE_ABSEIL=OFF
 
-      - name: Detect GCC toolchain for clang
-        id: gcc
-        run: |
-          GCC_VER=$(ls /usr/include/c++/ | grep -E '^[0-9]+$' | sort -n | tail -1)
-          echo "ver=${GCC_VER}" >> "$GITHUB_OUTPUT"
-
       - name: Run clang-tidy
         run: |
           find include/nexusfix -name '*.hpp' | \
             xargs clang-tidy-18 -p build --warnings-as-errors='*' \
               --extra-arg=-std=c++23 \
+              --extra-arg=-stdlib=libc++ \
               --extra-arg=-Iinclude \
-              --extra-arg=-isystem/usr/include/c++/${{ steps.gcc.outputs.ver }} \
-              --extra-arg=-isystem/usr/include/x86_64-linux-gnu/c++/${{ steps.gcc.outputs.ver }} \
               2>&1 | \
             tee clang-tidy-output.txt
           if grep -q 'error:' clang-tidy-output.txt; then

include/nexusfix/memory/mpsc_queue.hpp

@@ -34,6 +34,7 @@
 #include <new>
 
 #include "wait_strategy.hpp"
+#include "nexusfix/memory/buffer_pool.hpp"
 #include "nexusfix/util/compiler.hpp"
 
 #ifdef _MSC_VER

include/nexusfix/memory/seqlock.hpp

@@ -25,6 +25,7 @@
 #pragma once
 
 #include <atomic>
+#include <concepts>
 #include <cstdint>
 #include <new>
 #include <type_traits>

include/nexusfix/messages/fixt11/session.hpp

@@ -11,6 +11,7 @@
 #include "nexusfix/parser/field_view.hpp"
 #include "nexusfix/parser/runtime_parser.hpp"
 #include "nexusfix/messages/common/header.hpp"
+#include "nexusfix/messages/common/trailer.hpp"
 
 namespace nfx::fixt11 {
 

include/nexusfix/util/diagnostic.hpp

@@ -19,6 +19,7 @@
 #include <source_location>
 #include <cstdio>
 #include <cstdlib>
+#include <type_traits>
 
 namespace nfx::util {