util/*: Properly detect OpenBSD for pledge() call

The utils that are pledged checked HAVE_PLEDGE which was
bogus. OpenBSD defines __OpenBSD__, which you can check
for in ifdef.

This change makes nvmutil and spkmodem-recv *actually*
use pledge, when the utils are compiled on OpenBSD.

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

util/spkmodem_recv/spkmodem-recv.c

@@ -36,7 +36,7 @@ main(int argc, char *argv[])
 {
 	int c;
 
-#ifdef HAVE_PLEDGE
+#ifdef __OpenBSD__
 	if (pledge("stdio", NULL) == -1)
 		err(errno, "pledge");
 #endif