'let' init: don't check for octal until let builtin is tested ok
'let' init: don't check for octal until let builtin is tested ok

bin/modernish:
- Don't check for octal support in 'let' builtin until we know the
  builtin is a good ksh/bash/zsh-style 'let', otherwise we may get
  unexected output from a different 'let' builtin (FreeBSD sh).
  Fixes bug introduced by f94a7c0adcb4f926146abb9fea52e63aab7cad0b

modernish/modernish