use mysql_config --cflags output.

Makefile.am

@@ -7,14 +7,14 @@ noinst_HEADERS = mrnsys.h ha_mroonga.h
 
 plugin_LTLIBRARIES     = ha_groonga.la
 ha_groonga_la_LDFLAGS  = -module $(GROONGA_LIBS) $(MECAB_LIBS)
-ha_groonga_la_CXXFLAGS = $(AM_CFLAGS) -DMYSQL_DYNAMIC_PLUGIN
-ha_groonga_la_CFLAGS   = $(AM_CFLAGS) -DMYSQL_DYNAMIC_PLUGIN
+ha_groonga_la_CXXFLAGS = $(AM_CFLAGS) $(MYSQL_CFLAGS) -DMYSQL_DYNAMIC_PLUGIN
+ha_groonga_la_CFLAGS   = $(AM_CFLAGS) $(MYSQL_CFLAGS) -DMYSQL_DYNAMIC_PLUGIN
 ha_groonga_la_SOURCES  = ha_mroonga.cc mrnsys.c
 
 plugin_LIBRARIES                      = libgroonga_storage_engine.a
 libgroonga_storage_engine_a_LDFLANGS  = $(GROONGA_LIBS) $(MECAB_LIBS)
-libgroonga_storage_engine_a_CXXFLAGS  = $(AM_CFLAGS)
-libgroonga_storage_engine_a_CFLAGS    = $(AM_CFLAGS)
+libgroonga_storage_engine_a_CXXFLAGS  = $(AM_CFLAGS) $(MYSQL_CFLAGS)
+libgroonga_storage_engine_a_CFLAGS    = $(AM_CFLAGS) $(MYSQL_CFLAGS)
 libgroonga_storage_engine_a_SOURCES   = ha_mroonga.cc mrnsys.c
 
 SUBDIRS = test apt rpm yum doc

configure.ac

@@ -74,6 +74,7 @@ AC_DEFUN([CONFIG_OPTION_MYSQL],[
   fi
   MYSQL_INC="$MYSQL_INC $($ac_mysql_config --include)"
   ac_mysql_major_version="`$ac_mysql_config --version | cut -b 1,3`"
+  MYSQL_CFLAGS="$MYSQL_CFLAGS $($ac_mysql_config --cflags)"
   if test $ac_mysql_major_version -lt 55; then
     MYSQL_VERSION_CFLAGS="-DMYSQL51"
     AC_SUBST(MYSQL_VERSION_CFLAGS)
@@ -168,9 +169,10 @@ if test "$standalone_build" = "yes"; then
 else
   MYSQL_INC="-I../../sql -I../../include -I../../regex -I../.."
   plugindir="\$(pkglibdir)/plugin"
-  AC_SUBST(MYSQL_INC)
-  AC_SUBST(plugindir)
 fi
+AC_SUBST(MYSQL_INC)
+AC_SUBST(MYSQL_CFLAGS)
+AC_SUBST(plugindir)
 CONFIG_OPTION_MECAB
 CONFIG_OPTION_GROONGA