Add KERN_ARND and KERN_USERMOUNT to don't check list on OpenBSD

Author: wezm

libc-test/build.rs

@@ -431,6 +431,11 @@ fn main() {
             "KERN_KDENABLE_BG_TRACE" if apple => true,
             "KERN_KDDISABLE_BG_TRACE" if apple => true,
 
+            // These constants were removed in OpenBSD 6 (https://git.io/v7gBO
+            // https://git.io/v7gBq)
+            "KERN_USERMOUNT" |
+            "KERN_ARND" if openbsd => true,
+
             // These are either unimplemented or optionally built into uClibc
             "LC_CTYPE_MASK" | "LC_NUMERIC_MASK" | "LC_TIME_MASK" | "LC_COLLATE_MASK" | "LC_MONETARY_MASK" | "LC_MESSAGES_MASK" |
             "MADV_MERGEABLE" | "MADV_UNMERGEABLE" | "MADV_HWPOISON" | "IPV6_ADD_MEMBERSHIP" | "IPV6_DROP_MEMBERSHIP" | "IPV6_MULTICAST_LOOP" | "IPV6_V6ONLY" |