rts/package.conf.in: Fix CPP usage
rts/package.conf.in: Fix CPP usage

Summary:
The configure script sets `HAVE_LIBNUMA` to either `0` or `1` but this
file had `#ifdef HAVE_LIBNUMA`. This surfaced as a side-effect of
1050e46b5b. CPP is really hard to get right.

Test Plan: Validate on harbourmaster

Reviewers: simonmar, bgamari, austin, mpickering

Reviewed By: mpickering

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2631

mettekou/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,mettekou/ghc,sdiehl/ghc,ezyang/ghc,mettekou/ghc,olsner/ghc,mettekou/ghc,olsner/ghc,olsner/ghc,shlevy/ghc,mettekou/ghc,mettekou/ghc,olsner/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,olsner/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,olsner/ghc,ezyang/ghc,ezyang/ghc,olsner/ghc,sdiehl/ghc,mettekou/ghc