Add an IR-to-IR test for dwarf EH preparation using opt

This tests the simple resume instruction elimination logic that we have
before making some changes to it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229768 91177308-0d34-0410-b5e6-96231b3b80d8

tools/opt/opt.cpp

@@ -325,6 +325,7 @@ int main(int argc, char **argv) {
   initializeAtomicExpandPass(Registry);
   initializeRewriteSymbolsPass(Registry);
   initializeWinEHPreparePass(Registry);
+  initializeDwarfEHPreparePass(Registry);
 
 #ifdef LINK_POLLY_INTO_TOOLS
   polly::initializePollyPasses(Registry);