pgsql: Make pg_numa_query_pages() work in frontend programs

Make pg_numa_query_pages() work in frontend programs

It's currently only used in the server, but it was placed in src/port
with the idea that it might be useful in client programs too. However,
it will currently fail to link if used in a client program, because
CHECK_FOR_INTERRUPTS() is not usable in client programs. Fix that by
wrapping it in "#ifndef FRONTEND".

Reviewed-by: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
Discussion: https://www.postgresql.org/message-id/21cc7a48-99d9-4f69-9a3f-2c2de61ac8e5%40iki.fi
Backpatch-through: 18

Branch
------
REL_18_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/b08033944e7932265c4cb37cd19ceda2147e6cd7

Modified Files
--------------
src/port/pg_numa.c | 2 ++
1 file changed, 2 insertions(+)