[CMake] HP-UX ia64 (32bit) port

[Earle Lowe]

I have made an HP-UX port for CMAKE 3.15

It's not entirely optimal, because I took a small shortcut on fsevents
in libuv by using the "no events" source also used by cygwin. HP-UX
does have /dev/poll, so I think the AIX code could be used as a
template for a proper implementation.

It runs --version, but I haven't tried to use it to make itself again,
or any other tests.

HP-UX  B.11.31 ia64 using GCC 9.4.3

The binaries are 32-bit

I didn't do this quite correctly because I didn't fork master and I
don't have a PR prepared.

If the community wants though, I can make a proper merge request

I'll note, getting GCC 9.4.3 working on HP-UX is actually harder than
porting cmake. This version of GCC has a fairly robust implementation
of C++11

-Earle