util: remove the dependency on kcmp.h

Fixes: f76cbc7901 "util: Add os_same_file_description helper"

Acked-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3860>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3860>

src/util/os_file.c

@@ -34,11 +34,12 @@ os_file_create_unique(const char *filename, int filemode)
 #if defined(__linux__)
 
 #include <fcntl.h>
-#include <linux/kcmp.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 
+/* copied from <linux/kcmp.h> */
+#define KCMP_FILE 0
 
 static ssize_t
 readN(int fd, char *buf, size_t len)