Add a temporary solution to create a seedfile

This caused problems if a config with SHA512 was
compiled after a config without it and the seedfile
did not contain enough data.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/library/Makefile b/library/Makefile
index 54b0651..3b91e25 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -187,6 +187,7 @@
 endif
 
 static: libmbedcrypto.a libmbedx509.a libmbedtls.a
+	cd ../tests && echo "This is a seedfile that contains 64 bytes (65 on Windows)......" > seedfile
 
 shared: libmbedcrypto.$(DLEXT) libmbedx509.$(DLEXT) libmbedtls.$(DLEXT)