fix(ci): resolve macOS MySQL linkage check failures

Fix two issues in the MySQL linkage verification:

1. otool -L output includes the binary name on its first line, causing
   false positives when binaries are named mysql_backend_test. Skip the
   first line and match only against library dependency lines.

2. Brew's mariadb-connector-c is keg-only (not symlinked). Add
   CMAKE_PREFIX_PATH for macOS CI and add find_library/find_path
   fallback in CMakeLists.txt for system-installed libmariadb.

Author: kcenon

.github/workflows/ci.yml

@@ -345,6 +345,8 @@ jobs:
       if: runner.os == 'macOS'
       run: |
         brew install ninja googletest mariadb-connector-c
+        # mariadb-connector-c is keg-only; export paths for CMake discovery
+        echo "CMAKE_PREFIX_PATH=/opt/homebrew/opt/mariadb-connector-c" >> $GITHUB_ENV
 
     - name: Build and install common_system
       run: |
@@ -361,8 +363,13 @@ jobs:
 
     - name: Configure CMake with MySQL
       run: |
+        CMAKE_EXTRA_ARGS=""
+        if [ -n "$CMAKE_PREFIX_PATH" ]; then
+          CMAKE_EXTRA_ARGS="-DCMAKE_PREFIX_PATH=$CMAKE_PREFIX_PATH"
+        fi
         cmake -B build -G Ninja \
           -DCMAKE_BUILD_TYPE=Debug \
+          $CMAKE_EXTRA_ARGS \
           -DALLOW_BUILD_WITHOUT_NETWORK_SYSTEM=ON \
           -DUSE_THREAD_SYSTEM=OFF \
           -DUSE_MONITORING_SYSTEM=OFF \
@@ -393,12 +400,16 @@ jobs:
           DEPS=$(${{ matrix.check-cmd }} "$binary" 2>/dev/null || true)
           echo "$DEPS"
 
-          if echo "$DEPS" | grep -qi "mariadb\|mysql"; then
+          # Skip the first line of otool output (binary name) to avoid
+          # false positives from binary names like mysql_backend_test
+          DEPS_LIBS=$(echo "$DEPS" | tail -n +2)
+
+          if echo "$DEPS_LIBS" | grep -qiE "libmariadb|libmysqlclient"; then
             FOUND_BINARY=true
             echo "  -> libmariadb dependency detected"
 
             # Verify it is a shared library reference (not static)
-            if echo "$DEPS" | grep -qiE "libmariadb.*\.so|libmariadb.*\.dylib|libmysqlclient.*\.so|libmysqlclient.*\.dylib"; then
+            if echo "$DEPS_LIBS" | grep -qiE "libmariadb.*\.so|libmariadb.*\.dylib|libmysqlclient.*\.so|libmysqlclient.*\.dylib"; then
               echo "  -> PASS: dynamically linked (LGPL-2.1 compliant)"
             else
               echo "  -> FAIL: linkage type unclear, manual review needed"

database/CMakeLists.txt

@@ -420,9 +420,42 @@ if(USE_MYSQL)
             message(STATUS "  libmariadb linking: ${_mariadb_type} (verify dynamic linkage in CI)")
         endif()
     else()
-        message(WARNING "MariaDB Connector/C not found, disabling MySQL support")
-        message(STATUS "  libmariadb found: ${unofficial-libmariadb_FOUND}")
-        set(USE_MYSQL OFF CACHE BOOL "MySQL support disabled due to missing libraries" FORCE)
+        # Fallback: find system-installed libmariadb (Homebrew, apt, etc.)
+        # Brew's mariadb-connector-c is keg-only — requires CMAKE_PREFIX_PATH
+        find_library(MARIADB_LIBRARY NAMES mariadb mariadbclient
+            HINTS
+                /opt/homebrew/opt/mariadb-connector-c/lib
+                /usr/lib/x86_64-linux-gnu
+        )
+        find_path(MARIADB_INCLUDE_DIR NAMES mysql.h mariadb/mysql.h
+            HINTS
+                /opt/homebrew/opt/mariadb-connector-c/include/mariadb
+                /usr/include/mariadb
+        )
+
+        if(MARIADB_LIBRARY AND MARIADB_INCLUDE_DIR)
+            target_link_libraries(${PROJECT_NAME} PUBLIC ${MARIADB_LIBRARY})
+            target_include_directories(${PROJECT_NAME} PUBLIC ${MARIADB_INCLUDE_DIR})
+            target_compile_definitions(${PROJECT_NAME} PUBLIC USE_MYSQL)
+            message(STATUS "MySQL support enabled (via system MariaDB Connector/C, LGPL-2.1)")
+            message(STATUS "  libmariadb library: ${MARIADB_LIBRARY}")
+            message(STATUS "  libmariadb include: ${MARIADB_INCLUDE_DIR}")
+
+            # LGPL-2.1 compliance: system-installed libraries are typically shared
+            get_filename_component(_mariadb_ext "${MARIADB_LIBRARY}" EXT)
+            if(_mariadb_ext STREQUAL ".a" OR _mariadb_ext STREQUAL ".lib")
+                message(WARNING
+                    "libmariadb appears to be statically linked (${_mariadb_ext}). "
+                    "LGPL-2.1 compliance requires dynamic linking.")
+            else()
+                message(STATUS "  libmariadb linking: dynamic (${_mariadb_ext}, LGPL-2.1 compliant)")
+            endif()
+        else()
+            message(WARNING "MariaDB Connector/C not found, disabling MySQL support")
+            message(STATUS "  libmariadb found (vcpkg): ${unofficial-libmariadb_FOUND}")
+            message(STATUS "  libmariadb found (system): lib=${MARIADB_LIBRARY} inc=${MARIADB_INCLUDE_DIR}")
+            set(USE_MYSQL OFF CACHE BOOL "MySQL support disabled due to missing libraries" FORCE)
+        endif()
     endif()
 endif()