<fcntl.h> should get you the POSIX_FADV_* constants.

Change-Id: I9de8b840570b228308c12d72b7617b8758237fb8
diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index ffbbd47..f6a89ef 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -31,6 +31,7 @@
 
 #include <sys/cdefs.h>
 #include <sys/types.h>
+#include <linux/fadvise.h>
 #include <linux/fcntl.h>
 #include <unistd.h>  /* this is not required, but makes client code much happier */