Replace blake2b by sha512 (as it is not yet available on alpine

challenge/bin/adlin

@@ -17,7 +17,7 @@ token_generator() {
 	do
 	    echo -n :${d}
 	done
-    } | b2sum | cut -d ' ' -f 1
+    } | sha512sum | cut -d ' ' -f 1
 }
 
 # JSON token format helper