Turns out I wasn't building the syscall libraries. Do so.

plat/linux/libsys/creat.c

@@ -0,0 +1,13 @@
+/* $Source: /cvsroot/tack/Ack/plat/linux386/libsys/creat.c,v $
+ * $State: Exp $
+ * $Revision: 1.1 $
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include "libsys.h"
+
+int creat(const char* filename, int mode)
+{
+	return open(filename, O_CREAT|O_WRONLY|O_TRUNC, mode);
+}