Add OSX buildslave

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@221670 91177308-0d34-0410-b5e6-96231b3b80d8
Fix name of max_build to correctly be max_builds

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@221671 91177308-0d34-0410-b5e6-96231b3b80d8