Fix meson uuid header check so it works with MSVC

Fix meson uuid header check so it works with MSVC

The OSSP uuid.h file includes unistd.h, so to use it with MSVC we need to
include the postgres include directories so it picks up our version of
that in src/include/port/win32_msvc. Adjust the meson test accordingly.

Backported from commit 7c655a04a2, so we can build release 16 with UUID

per request from Marina Polyakova