expr: fix eager evaluation of parenthesized dead branches

[can1357]

uutils expr evaluates parenthesized subexpressions during parsing, so arithmetic errors in dead | and & branches are raised before short-circuiting. GNU parses those branches without forcing evaluation and only evaluates when the branch is actually needed.

Reproduction Steps

expr 1 '|' '(' 1 / 0 ')'
# Expected (GNU): exit 0, stdout "1", no stderr
# Actual (uutils): exit 2, stderr "expr: division by zero"

Impact

Guarded expressions can fail with hard errors instead of boolean results, which breaks GNU-compatible shell control flow and error handling.