Make the llvm-runtest function much more amenable by eliminating all the

Make the llvm-runtest function much more amenable by eliminating all the
global variables that needed to be passed in. This makes it possible to
add new global variables with only a couple changes (Makefile and llvm-dg.exp)
instead of touching every single dg.exp file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35918 91177308-0d34-0410-b5e6-96231b3b80d8