Override `time` from libc

Prior to this change, there were spurious build failures seen in Github
CI, especially on macOS builds, where one test out of ~2000 would fail
randomly. After adding an option to display the diagnostics, it was
determined that the failure was only in the tests that included the
timestamp. This was because the time call was returning different values
between `test_setup` and `pinelog_log_message`. Even though they may
have been called milliseconds apart, the time skew was enough to have a
1 second difference between the two returned values.

This change overrides the `time` method from libc, and returns a static
value. With this change, CI should work fine regardless of how slow the
tests run.

test_pinelog.c

@@ -34,6 +34,12 @@ static FILE *observed_stream_r;
 static char expected_output[1024];
 static size_t expected_len;
 
+time_t time(time_t *p)
+{
+    // Override the time function from libc
+    return 1636671600;
+}
+
 static void test_case(const char *desc, bool test)
 {
     test_id++;