<linux/limits.h> is Linux-only; use <limits.h>. Guard CLOCK_MONOTONIC_RAW,
CLOCK_REALTIME_COARSE, and CLOCK_MONOTONIC_COARSE which don't exist on OpenBSD.

Index: frontend/main.c
--- frontend/main.c.orig
+++ frontend/main.c
@@ -46,7 +46,7 @@
 #include <linux/input.h>
 #include <sys/time.h>
 #include <libdisplay-info/info.h>
-#include <linux/limits.h>
+#include <limits.h>
 
 #include "weston.h"
 #include <libweston/libweston.h>
@@ -865,9 +865,15 @@ clock_name(clockid_t clk_id)
 	static const char *names[] = {
 		[CLOCK_REALTIME] =		"CLOCK_REALTIME",
 		[CLOCK_MONOTONIC] =		"CLOCK_MONOTONIC",
+#ifdef CLOCK_MONOTONIC_RAW
 		[CLOCK_MONOTONIC_RAW] =		"CLOCK_MONOTONIC_RAW",
+#endif
+#ifdef CLOCK_REALTIME_COARSE
 		[CLOCK_REALTIME_COARSE] =	"CLOCK_REALTIME_COARSE",
+#endif
+#ifdef CLOCK_MONOTONIC_COARSE
 		[CLOCK_MONOTONIC_COARSE] =	"CLOCK_MONOTONIC_COARSE",
+#endif
 #ifdef CLOCK_BOOTTIME
 		[CLOCK_BOOTTIME] =		"CLOCK_BOOTTIME",
 #endif
