Summary:
There is no point to importing at -O0, since we won't inline. We should
also disable other cross-module optimizations.
(Plan to backport this fix to the 3.9 branch to fix PR30774)
Reviewers: pcc
Subscribers: johanengelen, mehdi_amini
Differential Revision: https://reviews.llvm.org/D25918
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285648 91177308-0d34-0410-b5e6-96231b3b80d8