gcc: changed to use cloog isl backend for the Graphite loop optimization

base/gcc/gcc.conf

@@ -134,6 +134,8 @@ if pkginstalled -f cloog && pkginstalled -f ppl; then
 	var_append extraconfopt ' ' "--with-ppl=$( pkgprefix -r ppl )"
 	var_append extraconfopt ' ' "--with-ppl-lib=$( pkgprefix -r libdir ppl )"
 	var_append extraconfopt ' ' "--with-ppl-include=$( pkgprefix -r includedir ppl )"
+	# use the cloog-isl backend
+	var_append extraconfopt ' ' "--enable-cloog-backend=isl"
 	var_append extraconfopt ' ' "--with-cloog=$( pkgprefix -r cloog )"
 	var_append extraconfopt ' ' "--with-cloog-lib=$( pkgprefix -r libdir cloog )"
 	var_append extraconfopt ' ' "--with-cloog-include=$( pkgprefix -r includedir cloog )"