hopefully sate the clang self host build, which is apparently

hopefully sate the clang self host build, which is apparently
instantiating some folding set stuff that GCC isn't, requiring
some types to not be incomplete.

I don't know if clang is right or wrong, but unbreaking the
bot is goodness.  Here's the broken build:
http://google1.osuosl.org:8011/builders/clang-x86_64-darwin10-selfhost/builds/1813/steps/compile.llvm.stage2/logs/stdio

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100418 91177308-0d34-0410-b5e6-96231b3b80d8