Move SafeStack to CodeGen.

It depends on the target machinery, that's not available for
instrumentation passes.

llvm-svn: 258942
diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
index fe1605a..dc60f3c 100644
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -329,6 +329,7 @@
   initializeRewriteSymbolsPass(Registry);
   initializeWinEHPreparePass(Registry);
   initializeDwarfEHPreparePass(Registry);
+  initializeSafeStackPass(Registry);
   initializeSjLjEHPreparePass(Registry);
 
 #ifdef LINK_POLLY_INTO_TOOLS