Question about cross compiling

Month ago i'm setting up successfully a cross compile environment for Teltonika RUT9XX.
With mips-openwrt-linux-gcc -o app main.c headers.h command I got a 48KB binary.
Now, after formatted my PC and setting up again, when I compiled the same source files I got a 2.9MB binary.

Using lddtree command I get for the 48KB application

lddtree -a old_app 
old_app => ./old_app (interpreter => /lib/ => not found => not found => not found

and for the 2.9MB application

lddtree -a new_app
new_app => ./new_app (interpreter => none)

What I'm doing wrong? I'm following the same instructions to setup the environment
Thanks in advance

Wasn't ucLibC removed from the master branch?

I don't know. I cross compile just once and today I recompiled to check that everything worked fine. I newbie on that