tests: posix: add a compile-and-run-only test for syslog

Ensure that we have code coverage for syslog and that it
can compiles and run with regular tests.

Signed-off-by: Christopher Friedt <[email protected]>

tests/posix/common/src/syslog.c

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2024, Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/posix/syslog.h>
+#include <zephyr/posix/unistd.h>
+#undef LOG_ERR
+#include <zephyr/ztest.h>
+
+#define N_PRIOS 8
+/* avoid clashing with Zephyr's LOG_ERR() */
+#define _LOG_ERR 3
+
+ZTEST(syslog, test_syslog)
+{
+	int prios[N_PRIOS] = {
+		LOG_EMERG,   LOG_ALERT,  LOG_CRIT, _LOG_ERR,
+		LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG,
+	};
+
+	openlog("syslog", LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_LOCAL7);
+	(void)setlogmask(LOG_MASK(-1));
+
+	for (size_t i = 0; i < N_PRIOS; ++i) {
+		syslog(i, "syslog priority %d", prios[i]);
+	}
+
+	closelog();
+
+	/* yield briefly to logging thread */
+	usleep(100000);
+}
+
+ZTEST_SUITE(syslog, NULL, NULL, NULL, NULL, NULL);