[skip ci] Temporarily disable split-sections on Windows.
This temporarily disabled split-sections again on Windows because
of the overhead in linking it introduces. Unfortunately because BFD
is so slow a testsuite run gets almost 2x slower. Simply linking
Hello World takes an unacceptable long time.
So for now, it'll be disabled as we look into different linkers such
Test Plan: ./validate
Reviewers: austin, bgamari
Subscribers: rwbarton, thomie
GHC Trac Issues: Trac #12913
Differential Revision: https://phabricator.haskell.org/D3731