toOwnedBundle

    pub fn toOwnedBundle(wip: *Wip, compile_log_text: []const u8) !ErrorBundle {
        const gpa = wip.gpa;
        if (wip.root_list.items.len == 0) {
            assert(compile_log_text.len == 0);
            // Special encoding when there are no errors.
            wip.deinit();
            wip.* = .{
                .gpa = gpa,
                .string_bytes = .empty,
                .extra = .empty,
                .root_list = .empty,
            };
            return empty;
        }

        const compile_log_str_index = if (compile_log_text.len == 0) 0 else str: {
            const str: u32 = @intCast(wip.string_bytes.items.len);
            try wip.string_bytes.ensureUnusedCapacity(gpa, compile_log_text.len + 1);
            wip.string_bytes.appendSliceAssumeCapacity(compile_log_text);
            wip.string_bytes.appendAssumeCapacity(0);
            break :str str;
        };

        wip.setExtra(0, ErrorMessageList{
            .len = @intCast(wip.root_list.items.len),
            .start = @intCast(wip.extra.items.len),
            .compile_log_text = compile_log_str_index,
        });
        try wip.extra.appendSlice(gpa, @as([]const u32, @ptrCast(wip.root_list.items)));
        wip.root_list.clearAndFree(gpa);

        try wip.string_bytes.shrinkToLen(gpa);
        try wip.extra.shrinkToLen(gpa);

        return .{
            .string_bytes = wip.string_bytes.toOwnedSliceAssert(),
            .extra = wip.extra.toOwnedSliceAssert(),
        };
    }