test/CodeGenCXX/dllexport.cpp: -O2 and -disable-llvm-optzns aren't nedded

We only need them on the dllimport.cpp test to make sure that we emit code
for available_externaly functions, and don't inline the IR.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209145 91177308-0d34-0410-b5e6-96231b3b80d8