Enable embed also on fpm on non zts

[DracoBlue]

EDIT 2023/06/25: for those searching for something like this: we rolled our own based on the official alpine packages for php at https://github.com/Endava/docker-php/tree/release/8.2-zts (it supports php 8.2 with zts and following).

#1104 added the flag to Debian-based CLI variants; in #1175 was this added for debian based ZTS variants. we use an alpine-based non-zts variant, and would benefit from this flag as well.

Also, NGiNX Unit, the use case scenario mentioned in #1104 - seems to work with ubuntu, but lacks alpine support because of missing embed in cli docker image. In #1355 (comment) it was requested to not add this flag to keep alpine cli image small, thus the idea is here to do it with the fpm image instead.

Refs #510 #939 #1175 #1355

[DracoBlue]

Update from 2023/06/25: For those searching for something like this: we rolled our own based on the official alpine packages for php (but adjusted so that we get zts builds) at https://github.com/Endava/docker-php/tree/release/8.2-zts (it supports php 8.2 with zts and following).