[ARM] Register ConstantIslands with the pass manager

This allows us to use -stop-before/-stop-after/-run-pass - we can now write
.mir tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294948 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed