V8 (9.5) has split the `v8.h` header

[targos]

See v8/v8@ec06bb6

It shouldn't directly impact the Node.js build because v8.h is still here and includes everything it had before, but at least https://github.com/nodejs/node/blob/master/tools/install.py will have to be changed.

[targos]

@nodejs/v8 is there something else that we need to care about? Should we keep using v8.h or try to move to the new smaller headers?

[verwaest]

You can keep using v8.h but using smaller headers can be much more efficient. While I don't expect much churn, if you wait a bit before switching over you might avoid having to update includes a few times over.