Fix GCC compiler errors in cpyext tests.

Author: fangerer

graalpython/com.oracle.graal.python.test/src/tests/cpyext/test_abstract.py

@@ -517,7 +517,8 @@ def compile_module(self, name):
             (iter({'a':0,'b':1,'c':2}),2)
         ),
         code='''PyObject* wrap_PyIter_Next(PyObject* iter, int n) {
-            for (int i = 0; i < n - 1; i++) {
+            int i;
+            for (i = 0; i < n - 1; i++) {
                 PyIter_Next(iter);
             } 
             return PyIter_Next(iter);

graalpython/com.oracle.graal.python.test/src/tests/cpyext/test_list.py

@@ -162,7 +162,8 @@ def compile_module(self, name):
         ),
         code='''PyObject* wrap_PyList_SetItem(Py_ssize_t capacity, Py_ssize_t idx, PyObject* new_item) {
             PyObject *newList = PyList_New(capacity);
-            for (Py_ssize_t i = 0; i < capacity; i++) {
+            Py_ssize_t i;
+            for (i = 0; i < capacity; i++) {
                 if (i == idx) {
                     PyList_SetItem(newList, i, new_item);
                 } else {