use m4 from system, when using bison

package/bison/Makefile

@@ -16,6 +16,8 @@ include ${TOPDIR}/mk/package.mk
 
 $(eval $(call PKG_template,BISON,${PKG_NAME},${PKG_VERSION}-${PKG_RELEASE},${PKG_DEPENDS},${PKG_DESCR},${PKG_SECTION}))
 
+XAKE_FLAGS+=		M4=m4
+
 post-install:
 	${INSTALL_DIR} ${IDIR_BISON}/usr/bin ${IDIR_BISON}/usr/share/bison
 	${INSTALL_BIN} ${WRKINST}/usr/bin/bison ${IDIR_BISON}/usr/bin