Skip anonymous iter optimization test for llvm

Mike pointed out that this test started failing for llvm. It's a test that
essentially greps the generated code to make sure the optimization fired. It's
greping the c code, so it needs to be skipped for llvm.
Merge pull request #1061 from ronawho/elim-anonymous-range-construction

Skip anonymous iter optimization test for llvm

Mike pointed out that this test started failing for llvm. It's a test that
essentially greps the generated code to make sure the optimization fired. It's
greping the c code, so it needs to be skipped for llvm.