The default hello world stripped with one codegen unit and panic=abort was 342kB both nightly and stable. Adding lto dropped it 42kB in stable and 40kB in nightly. Adding build-std and only building core did not reduce it any further in size.
I assume OP is taking about using -Zbuild-std on nightly. This will drop it much more.
I assume OP is taking about using -Zbuild-std on nightly. This will drop it much more.