Fix native CI: use leanc with explicit LibUUID paths

System clang++ compiles against glibc 2.39 headers which redirect
strtoull to __isoc23_strtoull (C23), but leanc's bundled older glibc
lacks that symbol. Switch back to leanc so compiled code matches the
glibc leanc links against. Provide LibUUID paths explicitly since
leanc's custom sysroot prevents cmake find_package from locating them.

Author: junjihashimoto

.github/workflows/ci.yml

@@ -26,8 +26,7 @@ jobs:
       run: |
         sudo apt-get update
         sudo apt-get install -y cmake build-essential nlohmann-json3-dev \
-          uuid-dev libssl-dev python3 python3-pip \
-          clang libc++-dev libc++abi-dev
+          uuid-dev libssl-dev python3 python3-pip
 
     - name: Install Lean via elan
       run: |
@@ -39,14 +38,18 @@ jobs:
 
     - name: Build C++ FFI library
       run: |
-        # Use system clang++ with -stdlib=libc++ so the FFI library's C++ ABI
-        # matches Lean's linker (which uses libc++, not libstdc++).
-        # Using leanc directly as cmake compiler breaks find_package for
-        # system libraries (LibUUID etc.) due to its custom sysroot.
+        # Use leanc (Lean's clang wrapper) so compiled code uses leanc's
+        # bundled glibc headers, matching the glibc leanc links against.
+        # System clang++ uses system glibc 2.39 headers which redirect
+        # strtoull→__isoc23_strtoull (C23), missing from leanc's older glibc.
+        # STATIC_LIBRARY skips link tests that fail with leanc's sysroot.
+        # LibUUID paths provided explicitly since leanc's sysroot hides them.
         cmake -S . -B build-cmake \
-          -DCMAKE_C_COMPILER=clang \
-          -DCMAKE_CXX_COMPILER=clang++ \
-          -DCMAKE_CXX_FLAGS="-stdlib=libc++"
+          -DCMAKE_C_COMPILER=leanc \
+          -DCMAKE_CXX_COMPILER=leanc \
+          -DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY \
+          -DLibUUID_INCLUDE_DIR=/usr/include \
+          -DLibUUID_LIBRARY=/usr/lib/x86_64-linux-gnu/libuuid.a
         cmake --build build-cmake
 
     - name: Build Lean kernel