Im has found, what even with --specs.nano.specs --specs.nosys.lib will link libgcc, if some dependencies request it (like some float operations).
With -nostdlib flag, compiler will throw out newlib-nano too and obiviusly fail on build.
So the question is - how to save ability to link newlib-nano, but get error if some entity request any code what newlib-nano havent, butlibgcc have?