fix(install): add BusyBox compatibility fallback (#1032)

Fixes #1027

BusyBox's install command does not support -C (compare), -b (backup),
or -S (backup suffix) flags. When these flags fail, fall back to:
1. Simple 'install -m 755' command
2. If install completely unavailable, use cp + chmod

This allows croc to be installed in minimal Docker containers like
debian:stable-slim, netshoot, alpine, etc. using the bash installer.

Co-authored-by: Murat Aslan <murataslan1@users.noreply.github.com>