Try to match the CPython extension cflags more closely

Makefile

@@ -328,8 +328,7 @@ run_unittests:: run_$1_unittests
 )
 endef
 
-override GDB_CMDS ?=
-override GDB_CMDS := --ex "set confirm off" --ex "handle SIGUSR2 pass nostop noprint" --ex run --ex "bt 20" $(GDB_CMDS)
+GDB_CMDS := $(GDB_PRE_CMDS) --ex "set confirm off" --ex "handle SIGUSR2 pass nostop noprint" --ex run --ex "bt 20" $(GDB_POST_CMDS)
 BR ?=
 ARGS ?=
 ifneq ($(BR),)
@@ -935,9 +934,9 @@ TEST_EXT_MODULE_NAMES := basic_test descr_test slots_test
 .PHONY: ext_pyston
 ext_pyston: $(TEST_EXT_MODULE_NAMES:%=$(TEST_DIR)/test_extension/%.pyston.so)
 $(TEST_DIR)/test_extension/%.pyston.so: $(TEST_DIR)/test_extension/%.o $(BUILD_SYSTEM_DEPS)
-	$(CLANG_EXE) -shared $< -o $@ -g
+	gcc -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-z,relro $< -o $@ -g
 $(TEST_DIR)/test_extension/%.o: $(TEST_DIR)/test_extension/%.c $(wildcard ./include/*.h) $(BUILD_SYSTEM_DEPS)
-	$(CLANG_EXE) -O2 -fPIC -Wimplicit -I./include -c $< -o $@ -g
+	gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -Wimplicit -I./include -c $< -o $@
 
 .PHONY: ext_pyston_selfhost dbg_ext_pyston_selfhost ext_pyston_selfhost_release
 ext_pyston_selfhost: pyston_dbg $(TEST_EXT_MODULE_NAMES:%=$(TEST_DIR)/test_extension/*.c)