decrease bloated binary size

native binary is huge, lets remove unused parts to reduce size. idea: we an `alter-var-root` unused vars to nil.

Size history:
- version 0.1.3 from on release page: `98,591,600` bytes (with graalvm 21.3.0)
- version 0.1.3 built locally: `82,711,760` bytes (with graalvm 21.3.0) (what is the reason for difference??)
- latest built locally: `82,846,928`

Start by examining how the native binary is built and where the unused vars mentioned in the issue are defined. Compare the local and release-page sizes, then verify that removing unused parts reduces the binary without breaking the interpreter or REPL.

Written by the indexing model from the issue text.