rts.cabal.in: force inclusion of findPtr/_findPtr symbol only with debug flag

Authored by alpmestan on Nov 22 2018, 10:47 AM.

Description

rts.cabal.in: force inclusion of findPtr/_findPtr symbol only with debug flag

The previous strategy caused problems on Windows, as pointed out
at [1]

[1]: https://phabricator.haskell.org/rGHC900c47f88784#133905

Reviewers: Phyx, bgamari, erikd, simonmar

Reviewed By: Phyx

Subscribers: rwbarton, carter

GHC Trac Issues: Trac #15671

Differential Revision: https://phabricator.haskell.org/D5356