Only test the return value in mktime_negyear

Testing for the errno is an optional requirement according to POSIX, and
FreeBSD doesn't document that errno would be set on failure with mktime

Submitted by: pho
Sponsored by: EMC / Isilon Storage Division

contrib/netbsd-tests/lib/libc/time/t_mktime.c

@@ -72,7 +72,12 @@ ATF_TC_BODY(mktime_negyear, tc)
 
 	errno = 0;
 	t = mktime(&tms);
+#if defined(__FreeBSD__)
+	/* Open Group says "and may set errno to indicate the error" */
+	ATF_REQUIRE(t == (time_t)-1);
+#else
 	ATF_REQUIRE_ERRNO(0, t != (time_t)-1);
+#endif
 }
 
 ATF_TC(timegm_epoch);