This is a follow up to #200815 and #184634.
The PCRE2 JIT SEAlloc does not support the `fork()` as announced in
their README [0]:
> If you are enabling JIT under SELinux environment you may also want to add
> --enable-jit-sealloc, which enables the use of an executable memory allocator
> that is compatible with SELinux. Warning: this allocator is experimental!
> It does not support fork() operation and may crash when no disk space is
> available. This option has no effect if JIT is disabled.
As a result using it in PHP can break apps and tools, it can only be
enabled under very specific context where you have a full picture of
what the PHP code is doing.
This contribution disables again the PCRE2 JIT SEAlloc and extends the
existing PHP/PCRE2 tests to make sure we do not enable it again by
mistake.
[0] https://www.pcre.org/readme.txt
