tests: Mock the mode_t variant of open

open has a second form with a mode_t argument. When mocking without this
argument a caller trying to O_CREAT would have their mode_t argument
discarded and a random stack variable would be used instead.

BUG=b:187647884
BRANCH=None
TEST=meson test

Change-Id: I8c134e6d36a248d0f51985e389085a9e585fb83d
Signed-off-by: Evan Benn <evanbenn@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/69263
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

tests/tests.h

@@ -16,6 +16,8 @@
 #ifndef TESTS_H
 #define TESTS_H
 
+#include <fcntl.h>
+
 /* helpers.c */
 void address_to_bits_test_success(void **state);
 void bitcount_test_success(void **state);