[arcmt] When migrating to ARC disable -Werror so as to only block migration
for "hard" ARC errors, not warnings.

rdar://11691437

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158781 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed