php8*: disable PCRE2 JIT SEAlloc to avoid crashes when forking

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

nixos/tests/php/pcre.nix

···
 let
   testString = "can-use-subgroups";
 in
-import ../make-test-python.nix ({ lib, php, ... }: {
+import ../make-test-python.nix ({ pkgs, lib, php, ... }: {
   name = "php-${php.version}-httpd-pcre-jit-test";
   meta.maintainers = lib.teams.php.members;
 
···
         '';
     };
   };
-  testScript = { ... }:
-    ''
+  testScript = let
+    # PCRE JIT SEAlloc feature does not play well with fork()
+    # The feature needs to either be disabled or PHP configured correctly
+    # More information in https://bugs.php.net/bug.php?id=78927 and https://bugs.php.net/bug.php?id=78630
+    pcreJitSeallocForkIssue = pkgs.writeText "pcre-jit-sealloc-issue.php" ''
+      <?php
+      preg_match('/nixos/', 'nixos');
+      $pid = pcntl_fork();
+      pcntl_wait($pid);
+    '';
+  in ''
       machine.wait_for_unit("httpd.service")
       # Ensure php evaluation by matching on the var_dump syntax
       response = machine.succeed("curl -fvvv -s http://127.0.0.1:80/index.php")
       expected = 'string(${toString (builtins.stringLength testString)}) "${testString}"'
       assert expected in response, "Does not appear to be able to use subgroups."
+      machine.succeed("${php}/bin/php -f ${pcreJitSeallocForkIssue}")
     '';
 })

pkgs/top-level/all-packages.nix

···
   php82 = callPackage ../development/interpreters/php/8.2.nix {
     stdenv = if stdenv.cc.isClang then llvmPackages.stdenv else stdenv;
     pcre2 = pcre2.override {
-      withJitSealloc = !stdenv.isDarwin;
+      withJitSealloc = false; # See https://bugs.php.net/bug.php?id=78927 and https://bugs.php.net/bug.php?id=78630
     };
   };
   php82Extensions = recurseIntoAttrs php82.extensions;
···
   php81 = callPackage ../development/interpreters/php/8.1.nix {
     stdenv = if stdenv.cc.isClang then llvmPackages.stdenv else stdenv;
     pcre2 = pcre2.override {
-      withJitSealloc = !stdenv.isDarwin;
+      withJitSealloc = false; # See https://bugs.php.net/bug.php?id=78927 and https://bugs.php.net/bug.php?id=78630
     };
   };
   php81Extensions = recurseIntoAttrs php81.extensions;
···
   php80 = callPackage ../development/interpreters/php/8.0.nix {
     stdenv = if stdenv.cc.isClang then llvmPackages.stdenv else stdenv;
     pcre2 = pcre2.override {
-      withJitSealloc = !stdenv.isDarwin;
+      withJitSealloc = false; # See https://bugs.php.net/bug.php?id=78927 and https://bugs.php.net/bug.php?id=78630
     };
   };
   php80Extensions = recurseIntoAttrs php80.extensions;