tests: Add workaround to allow tests mock fileno on FreeBSD

fileno can be a function and a macro in FreeBSD, depending on whether
the environment in multi-threaded or single-threaded. For single
thread, macro is used. Macro is expanded into a inline code which
accesses private field of file descriptor. This is impossible to
mock in tests.

Pretending that environment is multi-threaded makes fileno function
to be called instead of a macro. Function can be mocked for tests.

BUG=b:237606255
TEST=ninja test
tests pass on two environments:
1) FreeBSD 13.1-RELEASE-p2 GENERIC amd64
2) Debian 5.17.11 x86_64 GNU/Linux

Change-Id: I3789ea9107a4cf8033cf59bb96d3c82aa58de026
TICKET: https://ticket.coreboot.org/issues/411
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/67312
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Thomas Heijligen <src@posteo.de>
Reviewed-by: Peter Marheine <pmarheine@chromium.org>
---
M tests/tests.c
1 file changed, 41 insertions(+), 0 deletions(-)

diff --git a/tests/tests.c b/tests/tests.c
index 8e3fdde..7f20069 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -370,6 +370,17 @@
 {
 	int ret = 0;
 
+#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
+	/*
+	 * Pretending to be a multithreaded environment so that `fileno`
+	 * is called as a function (and not as a macro).
+	 * fileno macro in FreeBSD is expanded into inline access of
+	 * private field of file descriptor, which is impossible to mock.
+	 * Calling fileno as a function allows the test to mock it.
+	 */
+	__isthreaded = 1;
+#endif
+
 	if (argc > 1)
 		cmocka_set_test_filter(argv[1]);
 

