libreboot-utils: don't use the GNU SOURCE macro

use the POSIX one

declare prototypes where necessary.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/libreboot-utils/lib/rand.c

@@ -7,28 +7,21 @@
 #ifndef RAND_H
 #define RAND_H
 
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE 1
-#endif
-
 #ifdef __OpenBSD__
 #include <sys/param.h>
 #endif
 #include <sys/types.h>
 
-#ifndef USE_URANDOM
-#define USE_URANDOM 0
-#endif
-
-#include <errno.h>
 #if defined(USE_URANDOM) && \
     ((USE_URANDOM) > 0)
 #include <fcntl.h> /* if not arc4random: /dev/urandom */
 #elif defined(__linux__)
 #include <sys/random.h>
 #include <sys/syscall.h>
+long syscall(long number, ...);
 #endif
 
+#include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
 #include <stddef.h>