expr: Handle '$' at the end of an alternative pattern

Author: frendsick

src/uu/expr/src/syntax_tree.rs

@@ -188,6 +188,8 @@ impl StringOp {
                                 match pattern_chars.peek() {
                                     // End of a capturing group
                                     Some(')') => re_string.push('$'),
+                                    // End of an alternative pattern
+                                    Some('|') => re_string.push('$'),
                                     _ => re_string.push_str(r"\$"),
                                 }
                                 re_string.push(backslash);