Do not run -O3 to canonicalize test case

This is not only not necessary, but in case -03 changes this can actually
cause arbitrarily failing test cases such as, e.g., a recent change by Chandler
that caused -O3 to unroll the loop body, which made the loop we wanted to
detect disappear and consequently this test case fail.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@200204 91177308-0d34-0410-b5e6-96231b3b80d8