`PHP7DLLTS_EXPORTS` is not used throughout php-src, and it's unlikely
that it is used by any extension, especially since it still refers to
PHP 7. The symbol had been introduced in 2014[1], but is not even used
in latest PHP-7.4; probably it was just supposed to be used, or part of
phpng.
[1] <fc734cf95d>
Since CI already ran for the PR, we can now [skip ci].