add -fPIC for groonga-normalizer-mysql

storage/mroonga/vendor/groonga/vendor/plugins/groonga-normalizer-mysql/normalizers/CMakeLists.txt

@@ -17,6 +17,14 @@
 
 set(NORMALIZERS_DIR "${GROONGA_PLUGINS_DIR}/normalizers")
 read_file_list(${CMAKE_CURRENT_SOURCE_DIR}/mysql_sources.am MYSQL_SOURCES)
+
+if(NOT DEFINED CMAKE_C_COMPILE_OPTIONS_PIC)
+  # For old CMake
+  if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_COMPILER_IS_CLANGCXX)
+    check_build_flag("-fPIC")
+  endif()
+endif()
+
 if(GROONGA_NORMALIZER_MYSQL_EMBED)
   add_library(mysql_normalizer STATIC ${MYSQL_SOURCES})
   set_property(TARGET mysql_normalizer APPEND PROPERTY