[test] Add wrap flags after D61934.

https://reviews.llvm.org/D61934, committed as r362687, r363540, r363364
and r363147, made some emitted instruction nus/nsw. Add these falgs to
Polly's regression tests.

This should fix
    Polly :: Isl/CodeGen/partial_write_in_region_with_loop.ll
    Polly :: Isl/CodeGen/scev_expansion_in_nonaffine.ll

llvm-svn: 363599