V8's default thread-isolated allocator has a bug on x64 Linux.

It uses memory protection keys (see `man 7 pkeys`) to
write-protect JIT code memory but in a way that is currently
incompatible with how we use threads.

Specifically, pkey permissions are inherited by child threads.
Threads that are not descendants of the thread that allocates
the pkey default to "no permissions" for that pkey.

Concretely, if thread A creates the v8::Platform (and the pkey)
and write-protects memory, then later thread B tries to access
that memory, it segfaults due to the lack of permissions.

The fix on V8's side is conceptually easy - call
pkey_set(PKEY_DISABLE_WRITE) before accessing the memory,
to flip the permissions from "none" to "can read" - but
until it's actually fixed, disable thread-isolation.

Fixes: rubyjs/mini_racer#300
Refs: https://issues.chromium.org/issues/360909072

Disable use of Linux memory protection keys

2.7 and 3.0 are EOL

Node.js uses it to speed up fork & exec (stops V8 heap pages from
getting copied into the forked process; slow) but mini_racer also
supports fork & continue.

Disable madvise(MADV_DONTFORK)

It was at C++14 but newer versions of V8 require C++17.

Note the V8 version didn't change between 22.6.0 and 22.7.0

Refs: nodejs/node#54576