test: Add UniqueFD test

Add a unit test to exercise the API of the UniqueFD class.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>

test/meson.build

@@ -53,6 +53,7 @@ internal_tests = [
     ['threads',                         'threads.cpp'],
     ['timer',                           'timer.cpp'],
     ['timer-thread',                    'timer-thread.cpp'],
+    ['unique-fd',                       'unique-fd.cpp'],
     ['utils',                           'utils.cpp'],
 ]